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Cosmoparticle Physics and String Theory
Stockholm University, Faculty of Science, Department of Physics.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with phenomenological and theoretical aspects of cosmoparticle physics and string theory. There are many open questions in these topics. In connection with cosmology we would like to understand the detailed properties of dark matter, dark energy, generation of primordial perturbations, etc., and in connection with particle physics we would like to understand the detailed properties of models that stabilize the electroweak scale, for instance supersymmetry. At the same time, we also need to understand these issues in a coherent theoretical framework. Such a framework is offered by string theory.

In this thesis, I analyze the interplay between Higgs and dark matter physics in an effective field theory extension of the minimally supersymmetric standard model. I study a theory of modified gravity, where the graviton has acquired a mass, and show the explicit implementation of the Vainshtein mechanism, which allows one to put severe constraints on the graviton mass. I address the question of Planck scale corrections to inflation in string theory, and show how such corrections can be tamed. I study perturbations of warped throat regions of IIB string theory compactifications and classify allowed boundary conditions. Using this analysis, I determine the potential felt by an anti-D3-brane in such compactifications, using the explicit harmonic data on the conifold. I also address questions of perturbative quantum corrections in string theory and calculate one-loop corrections to the moduli space metric of Calabi-Yau orientifolds.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2012. , 107 p.
Keyword [en]
Supersymmetry, dark matter, cosmology, inflation, modifications of gravity, string theory, flux compactifications, perturbative string theory
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Physics
Identifiers
URN: urn:nbn:se:su:diva-74928ISBN: 978-91-7447-492-3 (print)OAI: oai:DiVA.org:su-74928DiVA: diva2:512995
Public defence
2012-05-02, sal FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows:  Paper 3: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.

Available from: 2012-04-10 Created: 2012-03-29 Last updated: 2012-03-30Bibliographically approved
List of papers
1. Neutralino Dark Matter in BMSSM Effective Theory
Open this publication in new window or tab >>Neutralino Dark Matter in BMSSM Effective Theory
Show others...
2009 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 08Article in journal (Refereed) Published
Abstract [en]

We study thermal neutralino dark matter in an effective field theory extension of the MSSM, called ``Beyond the MSSM'' (BMSSM) in Dine, Seiberg and Thomas (2007). In this class of effective field theories, the field content of the MSSM is unchanged, but the little hierarchy problem is alleviated by allowing small corrections to the Higgs/higgsino part of the Lagrangian. We perform parameter scans and compute the dark matter relic density. The light higgsino LSP scenario is modified the most; we find new regions of parameter space compared to the standard MSSM. This involves interesting interplay between the WMAP dark matter bounds and the LEP chargino bound. We also find some changes for gaugino LSPs, partly due to annihilation through a Higgs resonance, and partly due to coannihilation with light top squarks in models that are ruled in by the new effective terms.

Place, publisher, year, edition, pages
IOP Publishing, 2009
Keyword
supersymmetry and cosmology, dark matter theory
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-33940 (URN)10.1088/1475-7516/2009/08/035 (DOI)000270036800035 ()
Available from: 2009-12-30 Created: 2009-12-30 Last updated: 2017-12-12Bibliographically approved
2. Two-field high-scale inflation in a sub-Planckian region of field space
Open this publication in new window or tab >>Two-field high-scale inflation in a sub-Planckian region of field space
2010 (English)In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 81, no 10, 103535- p.Article in journal (Refereed) Published
Abstract [en]

We present a simple two-field model of inflation and show how to embed it in string theory as a straightforward generalization of axion monodromy models. Phenomenologically, the predictions are equivalent to those of chaotic inflation, and, in particular, include observably large tensor modes. The whole high-scale large-field inflationary dynamics takes place within a region of field space that is parametrically sub-Planckian in diameter, hence improving our ability to control quantum corrections and achieve slow-roll inflation.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-49912 (URN)10.1103/PhysRevD.81.103535 (DOI)000278146700048 ()
Note
authorCount :3Available from: 2010-12-21 Created: 2010-12-20 Last updated: 2017-12-11Bibliographically approved
3. Spherically Symmetric Solutions in Massive Gravity and Constraints from Galaxies
Open this publication in new window or tab >>Spherically Symmetric Solutions in Massive Gravity and Constraints from Galaxies
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, analytical solutions describing static and spherically symmetric sources in the decoupling limit of massive gravity are derived. We analyze the model parameter range and specify when a Vainshtein mechanism is possible. Furthermore, we use gravitational lensing and velocity dispersion data from galaxies to put constraints on the mass scale of the graviton. The result for the inverse graviton mass scale lambda_g = h/(2pi)/(c m_g), in units of the Hubble radius r_H=c/H_0, is of the order lambda_g/r_H > 0.01-0.02 at 95% confidence level.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-74919 (URN)
Available from: 2012-03-29 Created: 2012-03-29 Last updated: 2012-04-02Bibliographically approved
4. A Toolkit for Perturbing Flux Compactifications
Open this publication in new window or tab >>A Toolkit for Perturbing Flux Compactifications
2011 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 12, 053- p.Article in journal (Refereed) Published
Abstract [en]

We develop a perturbative expansion scheme for solving general boundary value problems in a broad class of type IIB flux compactifications. The background solution is any conformally Calabi-Yau compactification with imaginary self-dual (ISD) fluxes. Upon expanding in small deviations from the ISD solution, the equations of motion simplify dramatically: we find a simple basis in which the n-th order equations take a triangular form. This structure implies that the system can be solved iteratively whenever the individual, uncoupled equations can be solved. We go on to demonstrate the solution of the system for a general warped Calabi-Yau cone: we present an algorithm that yields an explicit Green’s function solution for all the supergravity fields, to any desired order, in terms of the harmonic functions on the base of the cone. Our results provide a systematic procedure for obtaining the corrections to a warped throat geometry induced by attachment to a compact bulk. We also present a simple method for determining the sizes of physical effects mediated through warped geometries.

Keyword
AdS-CFT Correspondence, Flux compactifications
National Category
Other Physics Topics Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-74806 (URN)10.1007/JHEP12(2011)053 (DOI)000298847200053 ()
Available from: 2012-03-27 Created: 2012-03-26 Last updated: 2017-12-07Bibliographically approved
5. Stabilizing Antibrane Pseudomoduli
Open this publication in new window or tab >>Stabilizing Antibrane Pseudomoduli
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In a KKLT compactification, an anti-D3-brane at the tip of a warped deformed conifold region plays the crucial role of contributing positive vacuum energy. This antibrane also gives rise to light moduli, corresponding to angular motion around the tip. Following the work of Aharony, Antebi, and Berkooz, we characterize the leading effects due to compactification that lift these potentially dangerous pseudomoduli.We show that the dominant contribution to the anti-D3-brane potential arises from nonperturbative effects stabilizing the K\"ahler moduli. In ten-dimensional supergravity, this contribution is mediated by perturbations of three-form flux. Incorporating these flux perturbations, we compute the leading contribution to the potential for angular motion of the anti-D3-brane. We show that the resulting mass is parametrically larger than that obtained in prior work. However, we give a conclusive demonstration that bulk effects cannot stabilize the antibrane moduli above the IR scale without severe fine tuning.

National Category
Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-74927 (URN)
Available from: 2012-03-29 Created: 2012-03-29 Last updated: 2012-03-30Bibliographically approved
6. One-loop Kahler Metric of Calabi-Yau Orientifolds
Open this publication in new window or tab >>One-loop Kahler Metric of Calabi-Yau Orientifolds
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We evaluate string one-loop contributions to the Kahler metric of closed string moduli in toroidal minimally supersymmetric (Calabi-Yau) orientifolds with D-branes. We focus on the poorly understood N = 1 contributions contributions that a priori receive contributions from all massive string states.

National Category
Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-74930 (URN)
Available from: 2012-03-29 Created: 2012-03-29 Last updated: 2012-03-30Bibliographically approved

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