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• 251.
Lund Univ, Dept Phys, SE-22100 Lund, Sweden.;GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany..
Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany.. CEA DSM CNRS IN2P3, GANIL, F-14076 Caen, France.. CSIC Univ Valencia, Inst Fis Corpuscular, E-46920 Valencia, Spain.. GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany.;Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany.. GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany.. Lund Univ, Dept Phys, SE-22100 Lund, Sweden.. GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany.;Univ Giessen, D-35392 Giessen, Germany.. Univ Padua, INFN Sez Padova, IT-35131 Padua, Italy.;Univ Padua, Dipartimento Fis, IT-35131 Padua, Italy.. CEA DSM CNRS IN2P3, GANIL, F-14076 Caen, France.. CSIC Univ Valencia, Inst Fis Corpuscular, E-46920 Valencia, Spain.. GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany.. CSNSM, F-91405 Orsay, France.. STFC Daresbury Lab, Warrington WA4 4AD, Cheshire, England.. CSNSM, F-91405 Orsay, France.. CSNSM, F-91405 Orsay, France.. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik. Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany.. GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany.. Univ Lyon, CNRS IN2P3, Inst Phys Nucl Lyon, F-69622 Villeurbanne, France..
Performance of the AGATA gamma-ray spectrometer in the PreSPEC set-up at GSI2016Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 806, s. 258-266Artikkel i tidsskrift (Fagfellevurdert)

In contemporary nuclear physics, the European Advanced GAmma Tracking Array (AGATA) represents a crucial detection system for cutting-edge nuclear structure studies. AGATA consists of highly segmented high-purity germanium crystals and uses the pulse-shape analysis technique to determine both the position and the energy of the y-ray interaction points in the crystals. It is the tracking algorithms that deploy this information and enable insight into the sequence of interactions, providing information on the full or partial absorption of the 7 ray. A series of dedicated performance measurements for an AGATA set-up comprising 21 crystals is described. This set-up was used within the recent PreSPEC-AGATA experimental campaign at the GSI Helmholtzzentrum fur Schwerionenforschung. Using the radioactive sources Co-56, Co-60 and Eu-152, absolute and normalized efficiencies and the peak-to-total of the array were measured. These quantities are discussed using different data analysis procedures. The quality of the pulse-shape analysis and the tracking algorithm are evaluated. The agreement between the experimental data and the Geant4 simulations is also investigated.

• 252.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Teoretisk fysik.
Pierced, Wrapped and Torn: Aspects of String Theory Compactifications2009Doktoravhandling, med artikler (Annet vitenskapelig)

An outstanding problem in physics is to find a unified framework for quantum mechanics and general relativity. This is required for a better understanding of black holes and the early cosmology of the universe. String theory provides such a unification. In this thesis, we study aspects of compactifications of type IIB string theory. In the first part of the thesis, we study four-dimensional black holes consisting of D3-branes wrapping cycles in the compact dimensions. We discuss the correspondence between these black holes, topological string theory and matrix models. We then study the influence of black holes on the stability of flux compactifications. In the second part of the thesis, we turn to investigations of the type IIB landscape, i.e. the collection of stable and metastable vacua obtained from flux compactifications on conformal Calabi-Yau manifolds. We show that monodromies are important for the topographic structure of the landscape. In particular we find that there are long series of continuously connected vacua in the complex structure moduli space of the internal manifold. We also use geometric transitions to connect the moduli spaces of different manifolds, and create longer series of vacua. Finally, we investigate the stability of string theory vacua by constructing semiclassical instantons. These results have implications for the population of the landscape by eternal inflation.

1. Deforming, revolving and resolving: New paths in the string theory landscape
Åpne denne publikasjonen i ny fane eller vindu >>Deforming, revolving and resolving: New paths in the string theory landscape
2008 (engelsk)Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 02, artikkel-id 016Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

In this paper we investigate the properties of series of vacua in the string theory landscape. In particular, we study minima to the flux potential in type IIB compactifications on the mirror quintic. Using geometric transitions, we embed its one-dimensional complex structure moduli space in that of another Calabi-Yau with h1,1 = 86 and h2,1 = 2. We then show how to construct infinite series of continuously connected minima to the mirror quintic potential by moving into this larger moduli space, applying its monodromies, and moving back. We provide an example of such series, and discuss their implications for the string theory landscape

##### Emneord
Superstring Vacua, Flux compactifications
##### Forskningsprogram
Teoretisk fysik
##### Identifikatorer
urn:nbn:se:uu:diva-100502 (URN)10.1088/1126-6708/2008/02/016 (DOI)000254764400096 ()
Tilgjengelig fra: 2009-04-01 Laget: 2009-04-01 Sist oppdatert: 2017-12-13bibliografisk kontrollert
2. The world next door: Results in landscape topography
Åpne denne publikasjonen i ny fane eller vindu >>The world next door: Results in landscape topography
2007 (svensk)Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 03, s. 080-Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

Recently, it has become clear that neighboring multiple vacua might have interesting consequences for the physics of the early universe. In this paper we investigate the topography of the string landscape corresponding to complex structure moduli of flux compactified type IIB string theory. We find that series of continuously connected vacua are common. The properties of these series are described, and we relate the existence of infinite series of minima to certain unresolved mathematical problems in group theory. Numerical studies of the mirror quintic serve as illustrating examples.

##### Emneord
Superstring Vacua, Flux compactifications, dS vacua in string theory
##### Identifikatorer
urn:nbn:se:uu:diva-13761 (URN)10.1088/1126-6708/2007/03/080 (DOI)000245922000080 ()
Tilgjengelig fra: 2008-01-25 Laget: 2008-01-25 Sist oppdatert: 2017-12-11bibliografisk kontrollert
3. Stability of flux vacua in the presence of charged black
Åpne denne publikasjonen i ny fane eller vindu >>Stability of flux vacua in the presence of charged black
2006 (engelsk)Inngår i: JHEP, Vol. 09, s. 069-Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

In this letter we consider a charged black hole in a flux compactification of type IIB string theory. Both the black hole and the fluxes will induce potentials for the complex structure moduli. We choose the compact dimensions to be described locally by a deformed conifold, creating a large hierarchy. We demonstrate that the presence of a black hole typically will not change the minimum of the moduli potential in a substantial way. However, we also point out a couple of possible loop-holes, which in some cases could lead to interesting physical consequences such as changes in the hierarchy.

##### Identifikatorer
urn:nbn:se:uu:diva-20261 (URN)
Tilgjengelig fra: 2006-12-06 Laget: 2006-12-06 Sist oppdatert: 2011-01-11
4. 4D black holes and holomorphic factorization of the 0A matrix model
Åpne denne publikasjonen i ny fane eller vindu >>4D black holes and holomorphic factorization of the 0A matrix model
2005 (engelsk)Inngår i: Journal of High Energy Physics, Vol. 0510, s. 046-Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

n this letter, we relate the free energy of the 0A matrix model to the sum of topological and anti-topological string amplitudes. For arbitrary integer multiples of the matrix model self-dual radius we describe the geometry on which the corresponding topological string propagates. This geometry is not the one that follows from the usual ground ring analysis, but in a sense its "holomorphic square root". Mixing of terms for different genus in the matrix model free energy yields one-loop terms compatible with type II strings on compact Calabi-Yau target spaces. As an application, we give an explicit example of how to relate the 0A matrix model free energy to that of a four-dimensional black hole in type IIB theory, compactified on a compact Calabi-Yau. Variables, Legendre transforms, and large classical terms on both sides match perfectly.

##### Identifikatorer
urn:nbn:se:uu:diva-79421 (URN)
Tilgjengelig fra: 2006-04-10 Laget: 2006-04-10 Sist oppdatert: 2011-01-11
5. Field dynamics and tunneling in a flux landscape
Åpne denne publikasjonen i ny fane eller vindu >>Field dynamics and tunneling in a flux landscape
2008 (engelsk)Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 78, nr 8, s. 0835341-08353423Artikkel i tidsskrift (Fagfellevurdert) Published
##### sted, utgiver, år, opplag, sider
American Physical Society, 2008
fysik
##### Identifikatorer
urn:nbn:se:uu:diva-100308 (URN)10.1103/PhysRevD.78.083534 (DOI)
Tilgjengelig fra: 2009-03-30 Laget: 2009-03-30 Sist oppdatert: 2017-12-13bibliografisk kontrollert
6. Obstacle to populating the string theory landscape
Åpne denne publikasjonen i ny fane eller vindu >>Obstacle to populating the string theory landscape
2008 (engelsk)Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 78, nr 12, s. 1235131-1235135Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

We construct domain walls and instantons in a class of models with coupled scalar fields, determining, in agreement with previous studies, that many such solutions contain naked timelike singularities. Vacuum bubble solutions of this type do not contain a region of true vacuum, obstructing the ability of eternal inflation to populate other vacua. We determine a criterion that potentials must satisfy to avoid the existence of such singularities and show that many domain wall solutions in type IIB string theory are singular.

##### sted, utgiver, år, opplag, sider
American Physical Society, 2008
##### Forskningsprogram
teoretisk fysik
##### Identifikatorer
urn:nbn:se:uu:diva-100500 (URN)10.1103/PhysRevD.78.123513 (DOI)
Tilgjengelig fra: 2009-04-01 Laget: 2009-04-01 Sist oppdatert: 2017-12-13bibliografisk kontrollert
• 253.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
Upgrade and validation of PHX2MCNP for criticality analysis calculations for spent fuel storage pools2010Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave

A few years ago Westinghouse started the development of a new method for criticality calculations for spent nuclear fuel storage pools called “PHOENIX-to–MCNP” (PHX2MCNP). PHX2MCNP transfers burn-up data from the code PHOENIX to use in MCNP in order to calculate the criticality. This thesis describes a work with the purpose to further validate the new method first by validating the software MCNP5 at higher water temperatures than room temperature and, in a second step, continue the development of the method by adding a new feature to the old script. Finally two studies were made to examine the effect from decay time on criticality and to study the possibility to limit the number of transferred isotopes used in the calculations.

MCNP was validated against 31 experiments and a statistical evaluation of the results was done. The evaluation showed no correlation between the water temperature of the pool and the criticality. This proved that MCNP5 can be used in criticality calculations in storage pools at higher water temperature.

The new version of the PHX2MCNP script is called PHX2MCNP version 2 and has the capability to distribute the burnable absorber gadolinium into several radial zones in one pin. The decay time study showed that the maximum criticality occurs immediately after the takeout from the reactor as expected.

The last study, done to evaluate the possibility to limit the isotopes transferred from PHOENIX to MCNP showed that Case A, a case with the smallest number of isotopes, is conservative for all sections of the fuel element. Case A, which contains only some of the actinides and the strongest absorber of the burnable absorbers gadolinium 155, could therefore be used in future calculations.

Finally, the need for further validation of the method is discussed.

• 254.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Estimation of flank wear growth on coated inserts2013Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave

The present work was conducted in Sandvik Coromant to enhance the knowledge and understanding of general flank wear growth and specifically in this case flank wear growth on the cutting edge of the coated (Ti(C, N)/ Al2O3/ TiN) tool inserts.

Reliable modeling of tool life is always a concern for machining processes. Numbers of wear models studies predicting the tool life length have been created throughout the metal-cutting history to better predict and thereby control the tool life span, which is a major portion of the total cost of machining.

A geometrical contact model defining the geometry of the flank wear growth on the cutting tool inserts was proposed and then compared with four suggested models, which estimates flank wear. The focus of this work is on the initial growth of flank wear process and thereby short cutting-time intervals are measured.

Wear tests on cutting tool inserts were performed after orthogonal turning of Ovako 825 B steel and were analysed by optical instrument, 3D optical imaging in Alicona InfiniteFocus and EDS in SEM. Force measurements for cutting speeds, Vc, 150, 200, and 250 m/min and feed rate, fn, 0.15 mm/rev were recorded as well.

Results show that initial flank wear land, VB, growth is dominated by sliding distance per cutting length for different cutting speeds. A good correlation between the geometrical contact model and estimation models is indentified. The cutting force measurements compared with the flank wear land show proportionality between two parameters. For the machining data in the present study the flank wear rate per sliding distance, dW/dL, is estimated to 2x1033/m).

• 255. Latina, Andrea
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Implications of a Curved Tunnel for the Main Linac of CLIC2006Inngår i: EPAC 2006 Proceedings, s. 864-866Artikkel i tidsskrift (Fagfellevurdert)
• 256.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Experimentell fysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. RWTH Aachen. argonne national laboratory, Chicago. argonne national laboratory, Chicago.
Analysis of structural order in Fe1‐xZrx thin amorphous films2014Konferansepaper (Annet vitenskapelig)
• 257. Lemasson, A.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik.
Pair and single neutron transfer with Borromean 8He2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 697, nr 5, s. 454-458Artikkel i tidsskrift (Fagfellevurdert)

Direct observation of the survival of 199Au residues after 2n transfer in the He 8 + Au 197 system and the absence of the corresponding 67Cu in the He 8 + Cu 65 system at various energies are reported. The measurements of the surprisingly large cross sections for 199Au, coupled with the integral cross sections for the various Au residues, is used to obtain the first model-independent lower limits on the ratio of 2n to 1n transfer cross sections from 8He to a heavy target. A comparison of the transfer cross sections for 6,8He on these targets highlights the differences in the interactions of these Borromean nuclei. These measurements for the most neutron-rich nuclei on different targets highlight the need to probe the reaction mechanism with various targets and represent an experimental advance towards understanding specific features of pairing in the dynamics of dilute nuclear systems.

• 258. Leyser, T. B.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Astronomi och rymdfysik.
Radio pumping of the ionosphere with orbital angular momentumInngår i: Physical Review Letters, ISSN 0031-9007Artikkel i tidsskrift (Fagfellevurdert)
• 259.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Radio Pumping of Ionospheric Plasma with Orbital Angular Momentum2009Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, nr 6, s. 065004-Artikkel i tidsskrift (Fagfellevurdert)

Experimental results are presented of pumping ionospheric plasma with a radio wave carrying orbital angular momentum (OAM), using the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. Optical emissions from the pumped plasma turbulence exhibit the characteristic ring-shaped morphology when the pump beam carries OAM. Features of stimulated electromagnetic emissions (SEE) that are attributed to cascading Langmuir turbulence are well developed for a regular beam but are significantly weaker for a ring-shaped OAM beam in which case upper hybrid turbulence dominates the SEE.

• 260.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Atomic diffusion and mixing in old stars II. Observations of stars in the globular cluster NGC 6397 with VLT/FLAMES-GIRAFFE2008Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 490, nr 2, s. 777-U82Artikkel i tidsskrift (Fagfellevurdert)

Context. Evolutionary trends in the surface abundances of heavier elements have recently been identified in the globular cluster NGC 6397 ([Fe/H] = -2), indicating the operation of atomic diffusion in these stars. Such trends constitute important constraints for the extent to which diffusion modifies the internal structure and surface abundances of solar-type, metal-poor stars.

Aims. We perform an independent check of the reality and size of abundance variations within this metal-poor globular cluster.

Methods. Observational data covering a large stellar sample, located between the cluster turn-off point and the base of the red giant branch, are homogeneously analysed. The spectroscopic data were obtained with the medium-high resolution spectrograph FLAMES/GIRAFFE on VLT-UT2 (R similar to 27 000). We derive independent effective-temperature scales from profile fitting of Balmer lines and by applying colour-T-eff calibrations to Stromgren uvby and broad-band BVI photometry. An automated spectral analysis code is used together with a grid of MARCS model atmospheres to derive stellar surface abundances of Mg, Ca, Ti, and Fe.

Results. We identify systematically higher iron abundances for more evolved stars. The turn-off point stars are found to have 0.13 dex lower surface abundances of iron compared to the coolest, most evolved stars in our sample. There is a strong indication of a similar trend in magnesium, whereas calcium and titanium abundances are more homogeneous. Within reasonable error limits, the obtained abundance trends are in agreement with the predictions of stellar structure models

• 261. Lueftinger, T.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Astronomi och rymdfysik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Astronomi och rymdfysik.
3D atmospheric structure of the prototypical roAp star HD 24712 (HR1217)2008Inngår i: Contributions of the Astronomical Observatory Skalnate Pleso, ISSN 1335-1842, Vol. 38, nr 2, s. 335-340Artikkel i tidsskrift (Fagfellevurdert)

The first analysis of the structure of the surface magnetic field of a rapidly oscillating Ap (roAp) star is presented. We obtain information about abundance distributions of a number of chemical elements on the surface of the prototypical roAp star HD 24712 and about magnetic field geometry. Inverting rotationally modulated spectra in Stokes parameters I and V obtained with the SOFIN spectropolarimeter attached to the NOT, we recover surface abundance structures of sixteen different chemical elements, including Mg, Ca, Sc, Ti, Cr, Fe, Co, Ni, Y, La, Ce, Pr, Nd, Gd, Tb, and Dy. Our analysis reveal a pure dipolar structure of the stellar magnetic field and surprising and unexpected correlations of the various elemental surface abundance structures to this field geometry. Stratification analysis at phases of both magnetic extrema enable us to obtain the vertical dimension in the atmosphere of HD 24712. High time resolved spectroscopic data and observations obtained with the MOST space photometer give us the possibility to compare (Luftinger, 2007) our results to detailed pulsational analysis.

• 262.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Weakly interacting massive particle diffusion in the solar system including solar depletion and its effect on Earth capture2004Inngår i: Physical Review D, ISSN 1550-7998, Vol. D69, s. 123505-1 -- 123505-18Artikkel i tidsskrift (Fagfellevurdert)
• 263.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
On the Search for High-Energy Neutrinos: Analysis of data from AMANDA-II2008Doktoravhandling, med artikler (Annet vitenskapelig)

A search for a diffuse flux of cosmic neutrinos with energies in excess of 1014 eV was performed using two years of AMANDA-II data, collected in 2003 and 2004. A 20% evenly distributed sub-sample of experimental data was used to verify the detector description and the analysis cuts. A very good agreement between this 20% sample and the background simulations was observed. The analysis was optimised for discovery, to a relatively low price in limit setting power. The background estimate for the livetime of the examined 80% sample is 0.035 ± 68% events with an additional 41% systematical uncertainty.

The total neutrino flux needed for a 5σ discovery to be made with 50% probability was estimated to 3.4 ∙ 10-7 E-2 GeV s-1 sr-1 cm-2 equally distributed over the three flavours, taking statistical and systematic uncertainties in the background expectation and the signal efficiency into account. No experimental events survived the final discriminator cut. Hence, no ultra-high energy neutrino candidates were found in the examined sample. A 90% upper limit is placed on the total ultra-high energy neutrino flux at 2.8 ∙ 10-7 E-2 GeV s-1 sr-1 cm-2, taking both systematical and statistical uncertainties into account. The energy range in which 90% of the simulated E-2 signal is contained is 2.94 ∙ 1014 eV to 1.54 ∙ 1018 eV (central interval), assuming an equal distribution over the neutrino flavours at the Earth. The final acceptance is distributed as 48% electron neutrinos, 27% muon neutrinos, and 25% tau neutrinos.

A set of models for the production of neutrinos in active galactic nuclei that predict spectra deviating from E-2 was excluded.

1. Light tracking through ice and water: Scattering and absorption in heterogeneous media with Photonics
Åpne denne publikasjonen i ny fane eller vindu >>Light tracking through ice and water: Scattering and absorption in heterogeneous media with Photonics
2007 (engelsk)Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 581, nr 3, s. 619-631Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

In the field of neutrino astronomy, large volumes of optically transparent matter like glacial ice, lake water, or deep ocean water are used as detector media. Elementary particle interactions are studied using in situ detectors recording time distributions and fluxes of the faint photon fields of Cherenkov radiation generated by ultra-relativistic charged particles, typically muons or electrons.

The Photonics software package was developed to determine photon flux and time distributions throughout a volume containing a light source through Monte Carlo simulation. Photons are propagated and time distributions are recorded throughout a cellular grid constituting the simulation volume, and Mie scattering and absorption are realised using wavelength and position dependent parameterisations. The photon tracking results are stored in binary tables for transparent access through ansi-c and c++ interfaces. For higher-level physics applications, like simulation or reconstruction of particle events, it is then possible to quickly acquire the light yield and time distributions for a pre-specified set of light source and detector properties and geometries without real-time photon propagation.

In this paper the Photonics light propagation routines and methodology are presented and applied to the IceCube and Antares neutrino telescopes. The way in which inhomogeneities of the Antarctic glacial ice distort the signatures of elementary particle interactions, and how Photonics can be used to account for these effects, is described.

##### Emneord
Numerical simulation, Optical properties, Monte Carlo method, Ray tracing, Optical, Neutrino detection
##### Identifikatorer
urn:nbn:se:uu:diva-97326 (URN)10.1016/j.nima.2007.07.143 (DOI)000251148000007 ()
Tilgjengelig fra: 2008-05-15 Laget: 2008-05-15 Sist oppdatert: 2017-12-14bibliografisk kontrollert
2. Weakly interacting massive particle diffusion in the solar system including solar depletion and its effect on Earth capture
Åpne denne publikasjonen i ny fane eller vindu >>Weakly interacting massive particle diffusion in the solar system including solar depletion and its effect on Earth capture
2004 Inngår i: Physical Review D, ISSN 1550-7998, Vol. D69, s. 123505-1 -- 123505-18Artikkel i tidsskrift (Fagfellevurdert) Published
##### Identifikatorer
urn:nbn:se:uu:diva-97327 (URN)
Tilgjengelig fra: 2008-05-15 Laget: 2008-05-15bibliografisk kontrollert
• 264.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Light tracking through ice and water: Scattering and absorption in heterogeneous media with Photonics2007Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 581, nr 3, s. 619-631Artikkel i tidsskrift (Fagfellevurdert)

In the field of neutrino astronomy, large volumes of optically transparent matter like glacial ice, lake water, or deep ocean water are used as detector media. Elementary particle interactions are studied using in situ detectors recording time distributions and fluxes of the faint photon fields of Cherenkov radiation generated by ultra-relativistic charged particles, typically muons or electrons.

The Photonics software package was developed to determine photon flux and time distributions throughout a volume containing a light source through Monte Carlo simulation. Photons are propagated and time distributions are recorded throughout a cellular grid constituting the simulation volume, and Mie scattering and absorption are realised using wavelength and position dependent parameterisations. The photon tracking results are stored in binary tables for transparent access through ansi-c and c++ interfaces. For higher-level physics applications, like simulation or reconstruction of particle events, it is then possible to quickly acquire the light yield and time distributions for a pre-specified set of light source and detector properties and geometries without real-time photon propagation.

In this paper the Photonics light propagation routines and methodology are presented and applied to the IceCube and Antares neutrino telescopes. The way in which inhomogeneities of the Antarctic glacial ice distort the signatures of elementary particle interactions, and how Photonics can be used to account for these effects, is described.

• 265.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Electronic structure of a thermoelectric material: CsBi4Te62008Inngår i: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 69, nr 9, s. 2274-2276Artikkel i tidsskrift (Fagfellevurdert)

We have calculated the electronic structure of CsBi4Te6 by means of first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital method. From our calculated electronic structure we have calculated the frequency dependent dielectric function. Our calculations shows that CsBi4Te6 a semiconductor with a band gap of 0.3 eV. The calculated dielectric function is very anisotropic. Our calculated density of state support the recent experiment of Chung et al. [Science 287 (2000) 10241 that CsBi4Te6 is a high performance thermoelectric material for low temperature applications. (C) 2008 Elsevier Ltd. All rights reserved.

• 266.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik.
Test of digital neutron-gamma discrimination with four different photomultiplier tubes for the NEutron Detector Array (NEDA)2014Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 767, s. 83-91Artikkel i tidsskrift (Fagfellevurdert)

A comparative study of the neutron-gamma discrimination performance of a liquid scintillator detector BC501A coupled to four different 5 in photomultiplier tubes (ET9390kb, R11833-100, XP4512 and R4144) was carried out Both the Charge Comparison method and the Integrated Rise-Time method were implemented digitally to discriminate between neutrons and gamma rays emitted by a Cf-252 source. In both methods, the neutron-gamma discrimination capabilities of the four photomultiplier tubes were quantitatively compared by evaluating their figure-of-merit values at different energy regions between 50 keVee and 1000 keVee. Additionally, the results were further verified qualitatively using time-of-flight to distinguish gamma rays and neutrons. The results consistently show that photomultiplier tubes R11833-100 and ET9390kb generally perform best regarding neutron-gamma discrimination with only slight differences in figure-of-merit values. This superiority can be explained by their relatively higher photoelectron yield, which indicates that a scintillator detector coupled to a photomultiplier tube with higher photoelectron yield tends to result in better neutron-gamma discrimination performance. The results of this work will provide reference for the choice of photomultiplier tubes for future neutron detector arrays like NEDA.

• 267.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Turbulence-Assisted Planetary Growth: Hydrodynamical Simulations of Accretion Disks and Planet Formation2009Doktoravhandling, med artikler (Annet vitenskapelig)

The current paradigm in planet formation theory is developed around a hierarquical growth of solid bodies, from interstellar dust grains to rocky planetary cores. A particularly difficult phase in the process is the growth from meter-size boulders to planetary embryos of the size of our Moon or Mars. Objects of this size are expected to drift extremely rapid in a protoplanetary disk, so that they would generally fall into the central star well before larger bodies can form.

In this thesis, we used numerical simulations to find a physical mechanism that may retain solids in some parts of protoplanetary disks long enough to allow for the formation of planetary embryos. We found that such accumulation can happen at the borders of so-called dead zones. These dead zones would be regions where the coupling to the ambient magnetic field is weaker and the turbulence is less strong, or maybe even absent in some cases. We show by hydrodynamical simulations that material accumulating between the turbulent active and dead regions would be trapped into vortices to effectively form planetary embryos of Moon to Mars mass.

We also show that in disks that already formed a giant planet, solid matter accumulates on the edges of the gap the planet carves, as well as at the stable Lagrangian points. The concentration is strong enough for the solids to clump together and form smaller, rocky planets like Earth. Outside our solar system, some gas giant planets have been detected in the habitable zone of their stars. Their wakes may harbour rocky, Earth-size worlds.

1. Global magnetohydrodynamical models of turbulence in protoplanetary disks: I. A cylindrical potential on a Cartesian grid and transport of solids
Åpne denne publikasjonen i ny fane eller vindu >>Global magnetohydrodynamical models of turbulence in protoplanetary disks: I. A cylindrical potential on a Cartesian grid and transport of solids
2008 (engelsk)Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 479, s. 883-901Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

Aims.We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to demonstrate that Cartesian codes are comparable to cylindrical and spherical ones in handling the magnetohydrodynamics of the disk simulations while offering advantages, such as the absence of a grid singularity, for certain applications, e.g., circumbinary disks and disk-jet simulations. Methods: We employ the Pencil Code, a 3D high-order finite-difference MHD code using Cartesian coordinates. We solve the equations of ideal MHD with a local isothermal equation of state. Planets and stars are treated as particles evolved with an N-body scheme. Solid boulders are treated as individual superparticles that couple to the gas through a drag force that is linear in the local relative velocity between gas and particle. Results: We find that Cartesian grids are well-suited for accretion disk problems. The disk-in-a-box models based on Cartesian grids presented here develop and sustain MHD turbulence, in good agreement with published results achieved with cylindrical codes. Models without an inner boundary do not show the spurious build-up of magnetic pressure and Reynolds stress seen in the models with boundaries, but the global stresses and alpha viscosities are similar in the two cases. We investigate the dependence of the magnetorotational instability on disk scale height, finding evidence that the turbulence generated by the magnetorotational instability grows with thermal pressure. The turbulent stresses depend on the thermal pressure obeying a power law of 0.24 ± 0.03, compatible with the value of 0.25 found in shearing box calculations. The ratio of Maxwell to Reynolds stresses decreases with increasing temperature, dropping from 5 to 1 when the sound speed was raised by a factor 4, maintaing the same field strength. We also study the dynamics of solid boulders in the hydromagnetic turbulence, by making use of 106 Lagrangian particles embedded in the Eulerian grid. The effective diffusion provided by the turbulence prevents settling of the solids in a infinitesimally thin layer, forming instead a layer of solids of finite vertical thickness. The measured scale height of this diffusion-supported layer of solids implies turbulent vertical diffusion coefficients with globally averaged Schmidt numbers of 1.0 ± 0.2 for a model with α≈10-3 and 0.78 ± 0.06 for a model with α≈10-1. That is, the vertical turbulent diffusion acting on the solids phase is comparable to the turbulent viscosity acting on the gas phase. The average bulk density of solids in the turbulent flow is quite low (ρp = 6.0×10-11 kg m-3), but in the high pressure regions, significant overdensities are observed, where the solid-to-gas ratio reached values as great as 85, corresponding to 4 orders of magnitude higher than the initial interstellar value of 0.01

##### Emneord
magnetohydrodynamics (MHD), accretion, accretion disks, instabilities, turbulence, solar system: formation, diffusion
##### Identifikatorer
urn:nbn:se:uu:diva-97999 (URN)10.1051/0004-6361:20077948 (DOI)000253454600026 ()
Tilgjengelig fra: 2009-02-05 Laget: 2009-02-05 Sist oppdatert: 2017-12-14bibliografisk kontrollert
2. Embryos grown in the dead zone: Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids
Åpne denne publikasjonen i ny fane eller vindu >>Embryos grown in the dead zone: Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids
2008 (engelsk)Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 491, nr 3, s. L41-L44Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

Context: In the borders of the dead zones of protoplanetary disks, the inflow of gas produces a local density maximum that triggers the Rossby wave instability. The vortices that form are efficient in trapping solids. Aims: We aim to assess the possibility of gravitational collapse of the solids within the Rossby vortices. Methods: We perform global simulations of the dynamics of gas and solids in a low mass non-magnetized self-gravitating thin protoplanetary disk with the Pencil Code. We use multiple particle species of radius 1, 10, 30, and 100 cm. The dead zone is modelled as a region of low viscosity. Results: The Rossby vortices excited in the edges of the dead zone are efficient particle traps. Within 5 orbits after their appearance, the solids achieve critical density and undergo gravitational collapse into Mars sized objects. The velocity dispersions are of the order of 10 m s-1 for newly formed embryos, later lowering to less than 1 m s-1 by drag force cooling. After 200 orbits, over 300 gravitationally bound embryos were formed, 20 of them being more massive than Mars. Their mass spectrum follows a power law of index -2.3 ± 0.2.

##### Emneord
Accretion, accretion disks; Instabilites; Stars: planetary systems: formation
##### Identifikatorer
urn:nbn:se:uu:diva-98000 (URN)10.1051/0004-6361:200810626 (DOI)000261152900001 ()
Tilgjengelig fra: 2009-02-05 Laget: 2009-02-05 Sist oppdatert: 2017-12-14bibliografisk kontrollert
3. Planet formation bursts at the borders of the dead zone in 2D numerical simulations of circumstellar disks
Åpne denne publikasjonen i ny fane eller vindu >>Planet formation bursts at the borders of the dead zone in 2D numerical simulations of circumstellar disks
2009 (engelsk)Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 497, nr 3, s. 869-888Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

Context: As accretion in protoplanetary disks is enabled by turbulent viscosity, the border between active and inactive (dead) zones constitutes a location where there is an abrupt change in the accretion flow. The gas accumulation that ensues triggers the Rossby wave instability, which in turn saturates into anticyclonic vortices. It has been suggested that the trapping of solids within them leads to a burst of planet formation on very short timescales. Aims: We study in the formation and evolution of the vortices in greater detail, focusing on the implications for the dynamics of embedded solid particles and planet formation. Methods: We performed two-dimensional global simulations of the dynamics of gas and solids in a non-magnetized thin protoplanetary disk with the Pencil code. We used multiple particle species of radius 1, 10, 30, and 100 cm. We computed the particles' gravitational interaction by a particle-mesh method, translating the particles' number density into surface density and computing the corresponding self-gravitational potential via fast Fourier transforms. The dead zone is modeled as a region of low viscosity. Adiabatic and locally isothermal equations of state are used. Results: The Rossby wave instability is triggered under a variety of conditions, thus making vortex formation a robust process. Inside the vortices, fast accumulation of solids occurs and the particles collapse into objects of planetary mass on timescales as short as five orbits. Because the drag force is size-dependent, aerodynamical sorting ensues within the vortical motion, and the first bound structures formed are composed primarily of similarly-sized particles. In addition to erosion due to ram pressure, we identify gas tides from the massive vortices as a disrupting agent of formed protoplanetary embryos. We find evidence that the backreaction of the drag force from the particles onto the gas modifies the evolution of the Rossby wave instability, with vortices being launched only at later times if this term is excluded from the momentum equation. Even though the gas is not initially gravitationally unstable, the vortices can grow to Q ≈ 1 in locally isothermal runs, which halts the inverse cascade of energy towards smaller wavenumbers. As a result, vortices in models without self-gravity tend to rapidly merge towards a m = 2 or m =1 mode, while models with self-gravity retain dominant higher order modes (m = 4 or m = 3) for longer times. Non-selfgravitating disks thus show fewer and stronger vortices. We also estimate the collisional velocity history of the particles that compose the most massive embryo by the end of the simulation, finding that the vast majority of them never experienced a collision with another particle at speeds faster than 1 m s-1. This result lends further support to previous studies showing that vortices provide a favorable environment for planet formation.

##### Emneord
accretion, accretion disks; hydrodynamics; instabilities; stars: planetary systems: formation; methods: numerical; turbulence
##### Identifikatorer
urn:nbn:se:uu:diva-98001 (URN)10.1051/0004-6361/200811265 (DOI)000265280500022 ()
Tilgjengelig fra: 2009-02-05 Laget: 2009-02-05 Sist oppdatert: 2017-12-14bibliografisk kontrollert
4. Standing on the shoulders of giants: Trojan Earths and vortex trapping in low mass self-gravitating protoplanetary disks of gas and solids
Åpne denne publikasjonen i ny fane eller vindu >>Standing on the shoulders of giants: Trojan Earths and vortex trapping in low mass self-gravitating protoplanetary disks of gas and solids
2009 (engelsk)Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 493, nr 3, s. 1125-1139Artikkel i tidsskrift (Fagfellevurdert) Published
##### Abstract [en]

Context: Centimeter and meter-sized solid particles in protoplanetary disks are trapped within long-lived, high-pressure regions, creating opportunities for collapse into planetesimals and planetary embryos. Aims: We aim to study the effect of the high-pressure regions generated in the gaseous disks by a giant planet perturber. These regions consist of gas retained in tadpole orbits around the stable Lagrangian points as a gap is carved, and the Rossby vortices launched at the edges of the gap. Methods: We performed global simulations of the dynamics of gas and solids in a low mass non-magnetized self-gravitating thin protoplanetary disk. We employed the Pencil code to solve the Eulerian hydro equations, tracing the solids with a large number of Lagrangian particles, usually 100 000. To compute the gravitational potential of the swarm of solids, we solved the Poisson equation using particle-mesh methods with multiple fast Fourier transforms. Results: Huge particle concentrations are seen in the Lagrangian points of the giant planet, as well as in the vortices they induce at the edges of the carved gaps. For 1 cm to 10 cm radii, gravitational collapse occurs in the Lagrangian points in less than 200 orbits. For 5 cm particles, a 2M planet is formed. For 10 cm, the final maximum collapsed mass is around 3M. The collapse of the 1 cm particles is indirect, following the timescale of gas depletion from the tadpole orbits. Vortices are excited at the edges of the gap, primarily trapping particles of 30 cm radii. The rocky planet that is formed is as massive as 17M, constituting a Super-Earth. Collapse does not occur for 40 cm onwards. By using multiple particle species, we find that gas drag modifies the streamlines in the tadpole region around the classical L4 and L5 points. As a result, particles of different radii have their stable points shifted to different locations. Collapse therefore takes longer and produces planets of lower mass. Three super-Earths are formed in the vortices, the most massive having 4.5M. Conclusions: A Jupiter-mass planet can induce the formation of other planetary embryos at the outer edge of its gas gap. Trojan Earth-mass planets are readily formed; although not existing in the solar system, might be common in the exoplanetary zoo.

##### Emneord
accretion, accretion disks; hydrodynamics; instabilities; methods: numerical; solar system: formation; planets and satellites: formation
##### Identifikatorer
urn:nbn:se:uu:diva-98002 (URN)10.1051/0004-6361:200810797 (DOI)000262641100033 ()
Tilgjengelig fra: 2009-02-05 Laget: 2009-02-05 Sist oppdatert: 2017-12-14bibliografisk kontrollert
• 268.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Embryos grown in the dead zone: Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids2008Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 491, nr 3, s. L41-L44Artikkel i tidsskrift (Fagfellevurdert)

Context: In the borders of the dead zones of protoplanetary disks, the inflow of gas produces a local density maximum that triggers the Rossby wave instability. The vortices that form are efficient in trapping solids. Aims: We aim to assess the possibility of gravitational collapse of the solids within the Rossby vortices. Methods: We perform global simulations of the dynamics of gas and solids in a low mass non-magnetized self-gravitating thin protoplanetary disk with the Pencil Code. We use multiple particle species of radius 1, 10, 30, and 100 cm. The dead zone is modelled as a region of low viscosity. Results: The Rossby vortices excited in the edges of the dead zone are efficient particle traps. Within 5 orbits after their appearance, the solids achieve critical density and undergo gravitational collapse into Mars sized objects. The velocity dispersions are of the order of 10 m s-1 for newly formed embryos, later lowering to less than 1 m s-1 by drag force cooling. After 200 orbits, over 300 gravitationally bound embryos were formed, 20 of them being more massive than Mars. Their mass spectrum follows a power law of index -2.3 ± 0.2.

• 269.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Standing on the shoulders of giants: Trojan Earths and vortex trapping in low mass self-gravitating protoplanetary disks of gas and solids2009Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 493, nr 3, s. 1125-1139Artikkel i tidsskrift (Fagfellevurdert)

Context: Centimeter and meter-sized solid particles in protoplanetary disks are trapped within long-lived, high-pressure regions, creating opportunities for collapse into planetesimals and planetary embryos. Aims: We aim to study the effect of the high-pressure regions generated in the gaseous disks by a giant planet perturber. These regions consist of gas retained in tadpole orbits around the stable Lagrangian points as a gap is carved, and the Rossby vortices launched at the edges of the gap. Methods: We performed global simulations of the dynamics of gas and solids in a low mass non-magnetized self-gravitating thin protoplanetary disk. We employed the Pencil code to solve the Eulerian hydro equations, tracing the solids with a large number of Lagrangian particles, usually 100 000. To compute the gravitational potential of the swarm of solids, we solved the Poisson equation using particle-mesh methods with multiple fast Fourier transforms. Results: Huge particle concentrations are seen in the Lagrangian points of the giant planet, as well as in the vortices they induce at the edges of the carved gaps. For 1 cm to 10 cm radii, gravitational collapse occurs in the Lagrangian points in less than 200 orbits. For 5 cm particles, a 2M planet is formed. For 10 cm, the final maximum collapsed mass is around 3M. The collapse of the 1 cm particles is indirect, following the timescale of gas depletion from the tadpole orbits. Vortices are excited at the edges of the gap, primarily trapping particles of 30 cm radii. The rocky planet that is formed is as massive as 17M, constituting a Super-Earth. Collapse does not occur for 40 cm onwards. By using multiple particle species, we find that gas drag modifies the streamlines in the tadpole region around the classical L4 and L5 points. As a result, particles of different radii have their stable points shifted to different locations. Collapse therefore takes longer and produces planets of lower mass. Three super-Earths are formed in the vortices, the most massive having 4.5M. Conclusions: A Jupiter-mass planet can induce the formation of other planetary embryos at the outer edge of its gas gap. Trojan Earth-mass planets are readily formed; although not existing in the solar system, might be common in the exoplanetary zoo.

• 270.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Planet formation bursts at the borders of the dead zone in 2D numerical simulations of circumstellar disks2009Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 497, nr 3, s. 869-888Artikkel i tidsskrift (Fagfellevurdert)

Context: As accretion in protoplanetary disks is enabled by turbulent viscosity, the border between active and inactive (dead) zones constitutes a location where there is an abrupt change in the accretion flow. The gas accumulation that ensues triggers the Rossby wave instability, which in turn saturates into anticyclonic vortices. It has been suggested that the trapping of solids within them leads to a burst of planet formation on very short timescales. Aims: We study in the formation and evolution of the vortices in greater detail, focusing on the implications for the dynamics of embedded solid particles and planet formation. Methods: We performed two-dimensional global simulations of the dynamics of gas and solids in a non-magnetized thin protoplanetary disk with the Pencil code. We used multiple particle species of radius 1, 10, 30, and 100 cm. We computed the particles' gravitational interaction by a particle-mesh method, translating the particles' number density into surface density and computing the corresponding self-gravitational potential via fast Fourier transforms. The dead zone is modeled as a region of low viscosity. Adiabatic and locally isothermal equations of state are used. Results: The Rossby wave instability is triggered under a variety of conditions, thus making vortex formation a robust process. Inside the vortices, fast accumulation of solids occurs and the particles collapse into objects of planetary mass on timescales as short as five orbits. Because the drag force is size-dependent, aerodynamical sorting ensues within the vortical motion, and the first bound structures formed are composed primarily of similarly-sized particles. In addition to erosion due to ram pressure, we identify gas tides from the massive vortices as a disrupting agent of formed protoplanetary embryos. We find evidence that the backreaction of the drag force from the particles onto the gas modifies the evolution of the Rossby wave instability, with vortices being launched only at later times if this term is excluded from the momentum equation. Even though the gas is not initially gravitationally unstable, the vortices can grow to Q ≈ 1 in locally isothermal runs, which halts the inverse cascade of energy towards smaller wavenumbers. As a result, vortices in models without self-gravity tend to rapidly merge towards a m = 2 or m =1 mode, while models with self-gravity retain dominant higher order modes (m = 4 or m = 3) for longer times. Non-selfgravitating disks thus show fewer and stronger vortices. We also estimate the collisional velocity history of the particles that compose the most massive embryo by the end of the simulation, finding that the vast majority of them never experienced a collision with another particle at speeds faster than 1 m s-1. This result lends further support to previous studies showing that vortices provide a favorable environment for planet formation.

• 271.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Teoretisk astrofysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Teoretisk astrofysik.
Global magnetohydrodynamical models of turbulence in protoplanetary disks: I. A cylindrical potential on a Cartesian grid and transport of solids2008Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 479, s. 883-901Artikkel i tidsskrift (Fagfellevurdert)

Aims.We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to demonstrate that Cartesian codes are comparable to cylindrical and spherical ones in handling the magnetohydrodynamics of the disk simulations while offering advantages, such as the absence of a grid singularity, for certain applications, e.g., circumbinary disks and disk-jet simulations. Methods: We employ the Pencil Code, a 3D high-order finite-difference MHD code using Cartesian coordinates. We solve the equations of ideal MHD with a local isothermal equation of state. Planets and stars are treated as particles evolved with an N-body scheme. Solid boulders are treated as individual superparticles that couple to the gas through a drag force that is linear in the local relative velocity between gas and particle. Results: We find that Cartesian grids are well-suited for accretion disk problems. The disk-in-a-box models based on Cartesian grids presented here develop and sustain MHD turbulence, in good agreement with published results achieved with cylindrical codes. Models without an inner boundary do not show the spurious build-up of magnetic pressure and Reynolds stress seen in the models with boundaries, but the global stresses and alpha viscosities are similar in the two cases. We investigate the dependence of the magnetorotational instability on disk scale height, finding evidence that the turbulence generated by the magnetorotational instability grows with thermal pressure. The turbulent stresses depend on the thermal pressure obeying a power law of 0.24 ± 0.03, compatible with the value of 0.25 found in shearing box calculations. The ratio of Maxwell to Reynolds stresses decreases with increasing temperature, dropping from 5 to 1 when the sound speed was raised by a factor 4, maintaing the same field strength. We also study the dynamics of solid boulders in the hydromagnetic turbulence, by making use of 106 Lagrangian particles embedded in the Eulerian grid. The effective diffusion provided by the turbulence prevents settling of the solids in a infinitesimally thin layer, forming instead a layer of solids of finite vertical thickness. The measured scale height of this diffusion-supported layer of solids implies turbulent vertical diffusion coefficients with globally averaged Schmidt numbers of 1.0 ± 0.2 for a model with α≈10-3 and 0.78 ± 0.06 for a model with α≈10-1. That is, the vertical turbulent diffusion acting on the solids phase is comparable to the turbulent viscosity acting on the gas phase. The average bulk density of solids in the turbulent flow is quite low (ρp = 6.0×10-11 kg m-3), but in the high pressure regions, significant overdensities are observed, where the solid-to-gas ratio reached values as great as 85, corresponding to 4 orders of magnitude higher than the initial interstellar value of 0.01

• 272.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för kärn- och partikelfysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för kärn- och partikelfysik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik.
The single-particle and collective features in the nuclei just above Sn-1322007Inngår i: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 38, nr 4, s. 1213-1218Artikkel i tidsskrift (Fagfellevurdert)

The Advanced Time Delayed method has been used to measure the lifetimes of excited states in the exotic nuclei Sb-134, Sb-135 and Te-136 populated in the beta decay of Sn-134, Sn-135 and Sn-136, respectively. High purity Sn beams were extracted at the ISOLDE separator using a novel production technique utilizing the molecular SnS+ beams to isolate Sn from contaminating other fission products. Among the new results we have identified the 1/2(+) state in Sb-135 and its E2 transition to the lower-lying 5/2(+) state was found to be surprisingly collective. This measurement represents also one of the first applications of the LaBr3 scintillator to ultra fast timing.

• 273.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för kärn- och partikelfysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik.
Selected properties of nuclei at the magic shell closures from the studies of E1, M1 and E2 transition rates2009Inngår i: AIP conference Proceedings, 2009, Vol. 1090, s. 5502-Konferansepaper (Fagfellevurdert)
• 274.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för kärn- och partikelfysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik.
Structure of heavy Fe nuclei at the point of transition at N ~ 372009Inngår i: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 40, s. 477-480Artikkel i tidsskrift (Fagfellevurdert)
• 275.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för kärn- och partikelfysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kärnfysik.
The single-particle and collective features in the nuclei just above 132Sn2007Inngår i: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 38, s. 1213-1218Artikkel i tidsskrift (Fagfellevurdert)
• 276. Mahato, Dip N.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
First principles study of nuclear quadrupole interactions in the molecular solid BF3 and the nature of binding between the molecules2007Inngår i: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 176, nr 1-3, s. 15-20Artikkel i tidsskrift (Fagfellevurdert)

The electronic structures and nuclear quadrupole interactions (NQI) of the F-19* (I= 5/2) state of F-19 nucleus in solid BF3 are studied using the first-principles Hartree-Fock-Roothaan procedure including many-body electron correlation effects. The calculated NQI parameters, F-19* quadrupole coupling constant (e(2)qQ) and asymmetry parameter eta, were found to be in satisfactory agreement with experiment for the solid state system, which gives confidence in the reliability of the calculated electronic structures in the solid and hence the factors found to influence the binding of the molecules in the solid. It was found that the intermolecular binding energy primarily arises from Van der Waals (VDW) interactions between the molecules resulting from intermolecular many-body effects, which counteract the repulsive interactions between the molecules arising from one-electron Hartree-Fock (HF) theory.

• 277.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
SuperIso v2.3: A program for calculating flavor physics observables in supersymmetry2009Inngår i: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 180, nr 9, s. 1579-1613Artikkel i tidsskrift (Fagfellevurdert)

We describe SuperIso v2.3 which is a public program for evaluation of flavor physics observables in the minimal supersymmetric extension of the Standard Model (MSSM). SuperIso v2.3, in addition to the isospin asymmetry of BKγ, which was the main purpose of the first version, incorporates new flavor observables such as the branching ratio of Bsμ+μ, the branching ratio of Bτντ, the branching ratio of BDτντ and the branching ratio of Kμνμ. The calculation of the branching ratio of BXsγ is also improved in this version, as it now includes NNLO Standard Model contributions in addition to partial NLO supersymmetric contributions. The program also computes the muon anomalous magnetic moment (g−2). Four sample models are included in the package, namely mSUGRA, NUHM, AMSB and GMSB. SuperIso uses a SUSY Les Houches Accord file (SLHA1 or SLHA2) as input, which can be either generated automatically by the program via a call to external spectrum calculators, or provided by the user. The calculation of the observables is detailed in the Appendices, where a suggestion for the allowed intervals for each observable is also provided.

• 278.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Institutionen för kärn- och partikelfysik, Högenergifysik.
Supersymmetric parameter constraints from isospin asymmetry in b ---> s gamma transitions2007Inngår i: Proceedings of 15th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY07), 2007Konferansepaper (Fagfellevurdert)
• 279.
Clermont Université, France.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Högenergifysik.
Flavor constraints on two-Higgs-doublet models with general diagonal Yukawa couplings2010Inngår i: Physical Review D - Particles, Fields, Gravitation and Cosmology, ISSN 1550-7998, Vol. 81, nr 3, s. 035016-Artikkel i tidsskrift (Fagfellevurdert)

We consider constraints from flavor physics on two-Higgs-doublet models (2HDM) with general, flavor-diagonal, Yukawa couplings. Analyzing the charged Higgs contribution to different observables, we find that $b\to s\gamma$ transitions and $\Delta M_{B_d}$ restrict the coupling $\lambda_{tt}$ of the top quark (corresponding to $\cot\beta$ in models with a $Z_2$ symmetry) to $|\lambda_{tt}|<1$ for $m_{H^+}\lesssim 500$ GeV. Stringent constraints from $B$ meson decays are obtained also on the other third generation couplings $\lambda_{bb}$ and $\lambda_{\tau\tau}$, but with stronger dependence on $m_{H^+}$. For the second generation, we obtain constraints on combinations of $\lambda_{ss}$, $\lambda_{cc}$, and $\lambda_{\mu\mu}$ from leptonic $K$ and $D_s$ decays.The limits on the general couplings are translated to the common 2HDM types I -- IV with a $Z_2$ symmetry, and presented on the $(m_{H^+},\tan\beta)$ plane. The flavor constraints are most excluding in the type II model which lacks a decoupling limit in $\tan\beta$. We obtain a lower limit $m_{H^+}\gtrsim 300$ GeV in models of type II and III, while no lower bound on $m_{H^+}$ is found for types I and IV.

• 280. Malesani, D.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Early Spectroscopic Identification of SN 2008D2009Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 692, nr 2, s. L84-L87Artikkel i tidsskrift (Fagfellevurdert)

SN 2008D was discovered while following up an unusually bright X-ray transient (XT) in the nearby spiral galaxy NGC 2770. We present early optical spectra ( obtained 1.75 days after the XT) which allowed the first identification of the object as a supernova ( SN) at redshift z = 0.007. These spectra were acquired during the initial declining phase of the light curve, likely produced in the stellar envelope cooling after shock breakout, and rarely observed. They exhibit a rather flat spectral energy distribution with broad undulations, and a strong, W-shaped feature with minima at 3980 and 4190 angstrom ( rest frame). We also present extensive spectroscopy and photometry of the SN during the subsequent photospheric phase. Unlike SNe associated with gamma-ray bursts, SN 2008D displayed prominent He features and is therefore of Type Ib.

• 281. Man, L. C. T.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
Influence of a surfactant on single ion track etching: preparing and manipulating cylindrical micro wires2007Inngår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 265, nr 2, s. 621-625Artikkel i tidsskrift (Fagfellevurdert)

The influence of the alkali resistant surfactant Dowfax 2A1 on single ion track etching in 30 μm polycarbonate foils is studied at low etch rate (5 M NaOH at 41.5 ± 2 °C) using electro conductivity measurements. At surfactant concentrations above 10−4 vol.% break-through times are predictable (Δt/t < 0.25). At high surfactant concentrations (0.1 vol.%) the formation of cylindrical channels is favoured. The shape of these channels (length  26 μm, diameter  1.8 μm) is verified by electro-replication and SEM observation of the resulting wires. Agreement of radii is better than 0.1 μm. Depending on the current limit set during electro replication compact or hollow cylinders can be obtained. A technique for localizing and manipulating individual micro wires by their head buds is described.

• 282.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Astronomi och rymdfysik.
On the Winds of Carbon Stars and the Origin of Carbon: A Theoretical Study2009Doktoravhandling, med artikler (Annet vitenskapelig)