arXiv subjects

Sanjay Siwach

Publications and source records attributed to Sanjay Siwach.

25 records · Page 2Linked to original sources

arXiv2007

The Electric Dipole Moment of the Nucleons in Holographic QCD

We introduce the strong CP-violation in the framework of AdS/QCD model and calculate the electric dipole moments of nucleons as well as the CP-violating pion-nucleon coupling. Our holographic estimate of the electric dipole moments gives for the neutron d_n=1.08 X 10^{-16} theta (e cm), which is comparable with previous estimates. We also predict that the electric dipole moment of the proton should be precisely the minus of the neutron electric dipole moment, thus leading to a new sum rule on the electric dipole moments of baryons.

hep-ph↗

arXiv2006

Time-dependent supergravity solutions in null dilaton background

A class of time dependent pp-waves with NS-NS flux in type IIA string theory is considered. The background preserves 1/4 supersymmetry and may provide a toy model of Big Bang cosmology with non trivial flux. At the Big Bang singularity in early past, the string theory is strongly coupled and Matrix string model can be used to describe the dynamics. We also construct some time dependent supergravity solutions for D-branes and analyze their supersymmetry properties.

hep-th↗

arXiv2006

Deformed conformal and super-Poincaré symmetries in the non-(anti)commutative spaces

Generators of the super-Poincaré algebra in the non-(anti)commutative superspace are represented using appropriate higher-derivative operators defined in this quantum superspace. Also discussed are the analogous representations of the conformal and superconformal symmetry generators in the deformed spaces. This construction is obtained by generalizing the recent work of Wess et al on the Poincaré generators in the $θ$-deformed Minkowski space, or by using the substitution rules we derived on the basis of the phase-space structures of non-(anti)commutative-space variables. Even with the nonzero deformation parameters the algebras remain unchanged although the comultiplication rules are deformed. The transformation of the fields under deformed symmetry is also discussed. Our construction can be used for systematic developments of field theories in the deformed spaces.

hep-th↗

arXiv2005

1/2 BPS Geometries of M2 Giant Gravitons

We construct the general 1/2 BPS M2 giant graviton solutions asymptotic to the eleven-dimensional maximally supersymmetric plane wave background, based on the recent work of Lin, Lunin and Maldacena. The solutions have null singularity and we argue that it is unavoidable to have null singularity in the proposed framework, although the solutions are still physically relevant. They involve an arbitrary function F(x) which is shown to have a correspondence to the 1/2 BPS states of the BMN matrix model. A detailed map between the 1/2 BPS states of both sides is worked out.

hep-th↗

arXiv2005

Note on Brane-antibrane Description of Non-extremal Black Holes

Recently a number of authors have used a system of branes and antibranes at finite temperature for microscopic modeling of non-extremal black holes in string theory. The entropy of the system is derived from the simplified assumption of decoupled gas of open strings on the stacks of branes and antibranes and extremizing the total entropy with respect to the number of branes (or antibranes). The resulting entropy differs from the supergravity entropy by a deficit factor. We give an intuitive explanation for the deficit factor. We treat the whole system as two stacks of branes and antibranes with a single copy of Yang-Mills gas common to both the stacks. This gives the answer in agreement with the supergravity.

hep-th↗

arXiv2004

Brane Solutions with/without Rotation in PP-wave Spacetime

We present two classes of brane solutions in pp-wave spacetime. The first class of branes with a rotation parameter are constructed in an exact string background with NS-NS and R-R flux. The spacetime supersymmetry is analyzed by solving the standard Killing spinor equations and is shown to preserve the same amount of supersymmetry as the case without the rotation. This class of branes do not admit regular horizon. The second class of brane solutions are constructed by applying a null Melvin twist to the brane solutions of flat spacetime supergravity. These solutions admit regular horizon. We also comment on some thermodynamic properties of this class of solutions.

hep-th↗

arXiv2004

A Description of multi Charged Black Holes in terms of Branes and Antibranes

We describe multicharged black holes in terms of branes and antibranes together with multiple copies of gas of massless excitations. Assuming that energies of these copies of gas are all equal, we find that the entropy of the brane antibrane configuration agrees with that of the multicharged black hole in supergravity approximation, upto a factor X. We find that X = 1 for a suitable normalisation which admits a simple empirical interpretation that the available gas energy is all taken by one single gas which is, in a sense, a certain superposition of the multiple copies; and that the brane tensions are decreased by a factor of 4. This interpretation renders superfluous the assumption of equal energies, which is unnatural from a physical point of view.

hep-th↗