6.3k citations
Counting papers with at most 25 authors, so collaboration author lists do not stand in for the people here.
- Kyoto UniversityJP16 papers
- Tokyo Institute of TechnologyJP10 papers
- Inter-University Centre for Astronomy and AstrophysicsIN9 papers
- The University of TokyoJP9 papers
- Jamia Millia IslamiaIN8 papers
- Özyeğin UniversityTR8 papers
- Yukawa Institute for Theoretical PhysicsJP8 papers
- Advanced Science Research CenterJP7 papers
- Japan Atomic Energy AgencyJP7 papers
- Astronomical Observatory of RomeIT6 papers
- The University of OsakaJP5 papers
- Jožef Stefan InstituteSI4 papers
24 papers · 1 filter
Scalar field stochastic dynamics in de Sitter spacetime from exact solutions of quantum deficient oscillators
Yuta Nasuda, Koki Tokeshi, Yuki Watanabe
The stochastic dynamics of a scalar field in de Sitter spacetime can be regarded as a non-perturbative diffusion process, to which exact distribution and correlation functions are…
Angles in Fuzzy Disc and Angular Noncommutative Solitons
Shinpei Kobayashi, Tsuguhiko Asakawa
The fuzzy disc, introduced by the authors of Ref.[1], is a disc-shaped region in a noncommutative plane, and is a fuzzy approximation of a commutative disc. In this paper we show t…
Noncommutative Solitons of Gravity
Tsuguhiko Asakawa, Shinpei Kobayashi
We investigate a three-dimensional gravitational theory on a noncommutative space which has a cosmological constant term only. We found various kinds of nontrivial solutions, by ap…
Prospects of inflation in delicate D-brane cosmology
Sudhakar Panda, M. Sami, Shinji Tsujikawa
We study D-brane inflation in a warped conifold background that includes brane-position dependent corrections for the nonperturbative superpotential. Instead of stabilizing the vol…
UV stable, Lorentz-violating dark energy with transient phantom era
Maxim Libanov, Eleftherios Papantonopoulos, Valery Rubakov +2
Phantom fields with negative kinetic energy are often plagued by the vacuum quantum instability in the ultraviolet region. We present a Lorentz-violating dark energy model free fro…
Realizing Scale-invariant Density Perturbations in Low-energy Effective String Theory
Zong-Kuan Guo, Nobuyoshi Ohta, Shinji Tsujikawa
We discuss the realization of inflation and resulting cosmological perturbations in the low-energy effective string theory. In order to obtain nearly scale-invariant spectra of den…
String-inspired cosmology: Late time transition from scaling matter era to dark energy universe caused by a Gauss-Bonnet coupling
Shinji Tsujikawa, M. Sami
The Gauss-Bonnet (GB) curvature invariant coupled to a scalar field can lead to an exit from a scaling matter-dominated epoch to a late-time accelerated expansion, which is att…
Dynamics of dark energy
Edmund J. Copeland, M. Sami, Shinji Tsujikawa
In this paper we review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating Universe. In particular we discuss…
General analytic formulae for attractor solutions of scalar-field dark energy models and their multi-field generalizations
Shinji Tsujikawa
We study general properties of attractors for scalar-field dark energy scenarios which possess cosmological scaling solutions. In all such models there exists a scalar-field domina…
Inflation from D3-brane motion in the background of D5-branes
Sudhakar Panda, M. Sami, Shinji Tsujikawa +1
We study inflation arising from the motion of a BPS D3-brane in the background of a stack of k parallel D5-branes. There are two scalar fields in this set up-- (i) the radion field…
Inflation and dark energy arising from geometrical tachyons
Sudhakar Panda, M. Sami, Shinji Tsujikawa
We study the motion of a BPS D3-brane in the NS5-brane ring background. The radion field becomes tachyonic in this geometrical set up. We investigate the potential of this geometri…
de Sitter thermodynamics and the braneworld
Gianluca Calcagni
The de Sitter thermodynamics of cosmological models with a modified Friedmann equation is considered, with particular reference to high-energy Randall-Sundrum and Gauss-Bonnet bran…
Dark energy and cosmological solutions in second-order string gravity
Gianluca Calcagni, Shinji Tsujikawa, M Sami
We study the cosmological evolution based upon a -dimensional action in low-energy effective string theory in the presence of second-order curvature corrections and a modulus sc…
The fate of (phantom) dark energy universe with string curvature corrections
M. Sami, Alexey Toporensky, Peter V. Tretjakov +1
We study the evolution of (phantom) dark energy universe by taking into account the higher-order string corrections to Einstein-Hilbert action with a fixed dilaton. While the prese…
Coupled dark energy: Towards a general description of the dynamics
Burin Gumjudpai, Tapan Naskar, M. Sami +1
In dark energy models of scalar-field coupled to a barotropic perfect fluid, the existence of cosmological scaling solutions restricts the Lagrangian of the field $\vp$ to $p=X g(X…
Properties of singularities in (phantom) dark energy universe
Shin'ichi Nojiri, Sergei D. Odintsov, Shinji Tsujikawa
The properties of future singularities are investigated in the universe dominated by dark energy including the phantom-type fluid. We classify the finite-time singularities into fo…
Constraints on Dirac-Born-Infeld type dark energy models from varying alpha
Mohammad R. Garousi, M. Sami, Shinji Tsujikawa
We study the variation of the effective fine structure constant alpha for Dirac-Born-Infeld (DBI) type dark energy models. The DBI action based on string theory naturally gives ris…
What is needed of a tachyon if it is to be the dark energy?
Edmund J. Copeland, Mohammad R. Garousi, M. Sami +1
We study a dark energy scenario in the presence of a tachyon field with potential and a barotropic perfect fluid. The cosmological dynamics crucially depends on the asym…
A unified approach to scaling solutions in a general cosmological background
Shinji Tsujikawa, M. Sami
Our ignorance about the source of cosmic acceleration has stimulated study of a wide range of models and modifications to gravity. Cosmological scaling solutions in any of these th…
Dilatonic ghost condensate as dark energy
Federico Piazza, Shinji Tsujikawa
We explore a dark energy model with a ghost scalar field in the context of the runaway dilaton scenario in low-energy effective string theory. We address the problem of vacuum stab…
Generation of electromagnetic fields in string cosmology with a massive scalar field on the anti D-brane
Mohammad R. Garousi, M. Sami, Shinji Tsujikawa
We study the generation of electromagnetic fields in a string-inspired scenario associated with a rolling massive scalar field on the anti-D3 branes of KKLT de Sitter vacua. Th…
Exact spectrum and partition function of SU(m|n) supersymmetric Polychronakos model
B. Basu-Mallick, H. Ujino, M. Wadati
By using the fact that Polychronakos-like models can be obtained through the `freezing limit' of related spin Calogero models, we calculate the exact spectrum as well as partition…
Critical coupling in (1+1)-dimensional light-front theory
Kazuto Oshima, Masanobu Yahiro
The spontaneous symmetry breaking in (1+1)-dimensional theory is studied with discretized light-front quantization, that is, by solving the zero-mode constraint equation. T…
de Rham cohomology of SO(n) and some related manifolds by supersymmetric quantum mechanics
Kazuto Oshima
We study supersymmetric quantum mechanics on RP_{n},SO(n),G_{2} and U(2) to examine Witten's Morse theory concretely. We confirm the simple instanton picture of the de Rham cohomol…