Papers by Grigoris Panotopoulos
Journal of Cosmology and Astroparticle Physics, 2016
Physical Review D Particles and Fields, Sep 27, 2010
We study a coupled quintessence model in which the interaction with the dark-matter sector is a f... more We study a coupled quintessence model in which the interaction with the dark-matter sector is a function of the quintessence potential. Such a coupling can arise from a field dependent mass term for the dark-matter field. The dynamical analysis of a standard quintessence potential coupled with the interaction explored here shows that the system possesses a late-time accelerated attractor. In light of these results, we perform a fit to the most recent Supernovae Ia, Cosmic Microwave Background, and Baryon Acoustic Oscillation data sets. Constraints arising from weak equivalence principle violation arguments are also discussed.
Journal of Cosmology and Astroparticle Physics, 2016
We compute the absorption cross section of space-time scalars on a static D2 rane, in global coor... more We compute the absorption cross section of space-time scalars on a static D2 rane, in global coordinates, wrapped on the S^2 of an AdS_2 X S^2 X CY_3 geometry. We discuss its relevance for the construction of the dual quantum mechanics of Calabi-Yau black holes.
Journal of Cosmology and Astroparticle Physics, 2015
We explore a scenario in the Next-to-Minimal-Supersymmetric-Standard-Model (NMSSM) with both a li... more We explore a scenario in the Next-to-Minimal-Supersymmetric-Standard-Model (NMSSM) with both a light O(10) GeV neutralino and a CP-odd Higgs boson with significant coupling to down-type fermions, evading all current B physics, LEP and WMAP bounds. Motivated by a possible slight lepton universality breaking hinted in Upsilon decays, we consider the effect of the mixing of eta(b) resonances with the pseudoscalar Higgs on the spin-dependent scattering neutralino cross section off nucleons. We conclude that this mechanism could be relevant provided that non-perturbative effects enhance the effective eta(b)-nucleon coupling, taking over velocity/q^2 suppression factors, perhaps giving a new insight into the current controversial situation concerning direct search experiments of dark matter.
Physics Letters B, 2009
In the present work the primordial Big-Bang Nucleosynthesis (BBN) and weakly interacting massive ... more In the present work the primordial Big-Bang Nucleosynthesis (BBN) and weakly interacting massive particle (WIMP) dark matter are discussed in a certain class of modified gravitational theories, namely f (R) ∼ R n gravity. The new gravitational model is characterized by a single parameter n.
Physical Review D, 2010
We study a coupled quintessence model in which the interaction with the dark matter sector is a f... more We study a coupled quintessence model in which the interaction with the dark matter sector is a function of the quintessence potential. Such a coupling can arise from a field dependent mass term for the dark matter field. The dynamical analysis of a standard quintessence potential coupled with the interaction explored here shows that the system possesses a late time accelerated attractor. In light of these results, we perform a fit to the most recent Supernovae Ia, Cosmic Microwave Background and Baryon Acoustic Oscillation data sets. Constraints arising from weak equivalence principle violation arguments are also discussed.
Journal of High Energy Physics, 2008
The axino dark matter hypothesis in RSII brane model is studied. Within the framework of CMSSM we... more The axino dark matter hypothesis in RSII brane model is studied. Within the framework of CMSSM we assume that the lightest neutralino or stau is the NLSP, and that the axino production has a single contribution from the NLSP decay. It is found that the axino can play the role of dark matter in the universe and we determine what the axino mass should be for different values of the five-dimensional Planck mass. An upper bound is obtained for the latter.
Journal of High Energy Physics, 2011
String theory constructions using D-brane physics offer a framework where ingredients like extra ... more String theory constructions using D-brane physics offer a framework where ingredients like extra abelian factors in the gauge group, more than one Higgs doublet and a generalized Green-Schwarz mechanism appear at the same time. Motivated by works towards the direction of obtaining the Standard Model in orientifold constructions, we study in the present work a Stueckelberg extension of the two-Higgs-doublet model. The distinctive features of our model are i) a sharp decay width for the heavy gauge boson, and ii) a charged Higgs boson having two main decay channels at tree level with equal branching ratios.
Journal of High Energy Physics, 2010
We compute the absorption cross section of space-time scalars on a static D2 brane, in global coo... more We compute the absorption cross section of space-time scalars on a static D2 brane, in global coordinates, wrapped on the S 2 of an AdS 2 × S 2 × CY 3 geometry. We discuss its relevance for the construction of the dual quantum mechanics of Calabi-Yau black holes.
Journal of High Energy Physics, 2010
The viability of a possible cosmological scenario is investigated. The theoretical framework is t... more The viability of a possible cosmological scenario is investigated. The theoretical framework is the constrained next-to-minimal supersymmetric standard model (cNMSSM), with a gravitino playing the role of the lightest supersymmetric particle (LSP) and a neutralino acting as the next-to-lightest supersymmetric particle (NLSP). All the necessary constraints from colliders and cosmology have been taken into account. For gravitino we have considered the two usual production mechanisms, namely out-of equillibrium decay from the NLSP, and scattering processes from the thermal bath. The maximum allowed reheating temperature after inflation, as well as the maximum allowed gravitino mass are determined.
Journal of Physics: Conference Series, 2010
The gravitino dark matter with neutralino NLSP hypothesis is investigated in the framework of NMS... more The gravitino dark matter with neutralino NLSP hypothesis is investigated in the framework of NMSSM. We have considered both the thermal and non-thermal gravitino production mechanisms, and we have taken into account all the collider and cosmological constraints. The maximum allowed reheating temperature after inflation, as well as the maximum allowed gravitino mass are determined.
Journal of Physics: Conference Series, 2011
In the present work a two-component dark matter model is studied adopting the degenerate scenario... more In the present work a two-component dark matter model is studied adopting the degenerate scenario in the R-parity conserving NMSSM. The gravitino LSP and the neutralino NLSP are extremely degenerate in mass, avoiding the BBN bounds and obtaining a high reheating temperature for thermal leptogenesis. In this model both gravitino (absolutely stable) and neutralino (quasi-stable) contribute to dark matter, and direct detection searches for neutralino are discussed. Points that survive all the constraints correspond to a singlino-like neutralino.
Journal of High Energy Physics, 2006
The role of brane-bulk energy exchange and of an induced gravity term on a single braneworld of n... more The role of brane-bulk energy exchange and of an induced gravity term on a single braneworld of negative tension and vanishing effective cosmological constant is studied. It is shown that for the physically interesting cases of dust and radiation a unique global attractor which can realize our present universe (accelerating and 0 < Ωm0 < 1) exists for a wide range of the parameters of the model. For Ωm0 = 0.3, independently of the other parameters, the model predicts that the equation of state for the dark energy today is wDE,0 = −1.4, while Ωm0 = 0.03 leads to wDE,0 = −1.03. In addition, during its evolution, wDE crosses the wDE = −1 line to smaller values.
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Papers by Grigoris Panotopoulos