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Phenomenology of heterotic and type II orientifold string modelsMayes, Van Eric 15 May 2009 (has links)
Cryptons are metastable bound states of fractionally-charged particles that arise generically in the hidden sectors of models derived from heterotic string. We study their properties and decay modes in a specific flipped SU(5) model with long-lived four-particle spin-zero bound states called tetrons. The expected masses and lifetimes of the neutral tetrons make them good candidates for cold dark matter (CDM), and a potential source of the ultra-high energy cosmic rays (UHECRs) which have been observed, whereas the charged tetrons would have decayed in the early Universe.
We calculate the spectra of ultra-high-energy cosmic rays (UHECRs) in an ex¬plicit top-down model based on the decays of metastable neutral ‘crypton’ states. For all the decay operators, the total UHECR spectra are compatible with the available data. Also, the fractions of photons are compatible with all the published upper limits, but may be detectable in future experiments.
We also construct several intersecting D-brane models on a variety of orientifold backgrounds. In particular, we construct flipped SU(5), Pati-Salam, and MSSM-like models. The phenomenological properties of these models are studied. For one model in particular, we find that we may explain the quark masses and mixings, the tau lepton mass, and generate small neutrino masses via the see-saw mechanism.
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Monodromies of torsion D-branes on Calabi-Yau manifolds: extending the Douglas, et al., programMahajan, Rahul Saumik 28 August 2008 (has links)
Not available / text
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Linear perturbations of type IIB SUGRA in flux compactificationsCownden, Bradley 08 January 2015 (has links)
We consider linear perturbations of the background type IIB SUGRA solutions and find the equations of motion for the moduli. In particular, we allow for spacetime fluctuations of the positions of D3-branes in the compact dimensions. We postulate an ansatz for the 5-form flux due to the motion of the D3-branes, and a corresponding first-order part of the metric. The movement of the D3-branes is then shown to affect the warp factor at linear order. Using the equations of motion for the D3-branes, the universal volume modulus, and the universal axion, we construct a second-order, effective action. Finally, based on the form of the effective action, we examine a Kahler potential for the moduli space.
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Effective actions and charges of D-branes in curved space-time /Dawson, Peter Dale. January 2003 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 2003. / Bibliography: leaves 181-190.
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Monodromies of torsion D-branes on Calabi-Yau manifolds extending the Douglas, et al., program /Mahajan, Rahul Saumik. January 2002 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.
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A resolution of unnatural inflation in string theory? D-terms on the resolved conifold /Sully, James, January 1900 (has links)
Thesis (M.Sc.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2009/09/07). Includes bibliographical references.
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D-branes and orientifolds in calabi-yau compactificationsGarcia-Raboso, Alberto. January 2008 (has links)
Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Physics and Astronomy." Includes bibliographical references (p. 79-86).
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Higher dimensional gravity, black holes and brane worlds : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics in the University of Canterbury /Carter, Benedict. January 2006 (has links)
Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (p. 118-135). Also available via the World Wide Web.
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Compactificação alternativa de dimensões extras em gravitação de Brans-DickeHoff da Silva, Julio Marny [UNESP] 08 September 2009 (has links) (PDF)
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000857124.pdf: 627376 bytes, checksum: bab7d2e22364aa310b0479d830d3af44 (MD5) / After a brief introduction of some gravitational aspects of the Randall-Sundrum braneworld model as well as of the Brans-Dicke (BD) gravity, we propose two braneworld models using the, local and global, cosmic strings in the BD framework in order to generate all the bulk/brane structure. The final scenario is composed, in both cases, of a warped 4-brane with topology 'R POT. 4' x 'S POT. 1' and one extra dimension transverse to the brane. After that, we analyze the founded models in the scope of the Gauss-Codazzi formalism, with and without the imposition of 'Z IND. 2' symmetry on the brane
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Compactificação alternativa de dimensões extras em gravitação de Brans-Dicke /Hoff da Silva, Julio Marny. January 2009 (has links)
Orientador: Maria Cristina Batoni Abdalla Ribeiro / Coorientador: Maria Emília Xavier Guimarães / Banca: Roldão da Rocha Júnior / Banca: Antonio José Accioly / Banca: Maria Emilia Xavier Guimarães / Banca: Jorge Zanelli / Resumo:Após uma breve introdução acerca de alguns aspectos gravitacionais do modelo de Randall-Sundrum bem como da gravitação de Brans-Dicke (BD), propomos dois modelos de branas utilizando cordas cósmicas, local e global, em teoria de BD para a geração de toda a estrutura bulk/brana. O cenário final é composto, em ambos os casos, de um 4-brana warped com topologia 'R POT. 4' x 'S POT. 1' e uma dimensão extra transversa à brana. Após isso, analisamos os modelos encontrados no contexto do formalismo de Gauss-Codazzi, com e sem a imposição de simetria 'Z IND. 2', sobre a brana / Abstract: After a brief introduction of some gravitational aspects of the Randall-Sundrum braneworld model as well as of the Brans-Dicke (BD) gravity, we propose two braneworld models using the, local and global, cosmic strings in the BD framework in order to generate all the bulk/brane structure. The final scenario is composed, in both cases, of a warped 4-brane with topology 'R POT. 4' x 'S POT. 1' and one extra dimension transverse to the brane. After that, we analyze the founded models in the scope of the Gauss-Codazzi formalism, with and without the imposition of 'Z IND. 2' symmetry on the brane / Doutor
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