290 research outputs found

### Higher Derivative Terms in Three Dimensional Supersymmetric Theories

In this work, we systematically analyze higher derivative terms in the
supersymmetric effective actions for three dimensional scalar field theories
using $\mathcal{N} =1$ superspace formalism. In these effective actions, we
show that auxiliary fields do not propagate and their effective actions can be
expressed in terms of the physical fields. So, the theory does not change its
field content upon addition of higher derivative terms. We use derivative
expansion to generate four, five and six dimensional terms for an interacting
scalar field theory with $\mathcal{N} =1$ supersymmetry. We show that along
with pure fermionic and bosonic terms, there are various five and six
dimensional topological terms that mix bosonic and fermionic fields. Finally,
we use these results to obtain higher derivative topological terms in the
effective action for two M2-branes.Comment: 18 pages, 0 figures, Accepted for publication in JHE

### Four Dimensional Supersymmetric Theories in Presence of a Boundary

In this paper, we study $\mathcal{N} =1$ supersymmetric theories in four
dimensions in presence of a boundary. We demonstrate that it is possible to
preserve half the supersymmetry of the original theory by suitably modifying it
in presence of a boundary. This is done by adding new boundary terms to the
original action, such that the supersymmetric variation of the new terms
exactly cancels the boundary terms generated by the supersymmetric
transformation of the original bulk action. We also analyze the boundary
projections of such supercharges used in such a theory. We study
super-Yang-Mills theories in presence of a boundary using these results.
Finally, we study the Born-Infeld action in presence of a boundary. We analyse
the boundary effects for the Born-Infeld action coupled to a background dilaton
and an axion field. We also analyse the boundary effects for an non-abelian
Born-Infeld action. We explicitly construct the actions for these systems in
presence of a boundary. This action preserves half of the original
supersymmetry.Comment: 18 pages, no figures, Accepted for publication in Phys. Lett.

### Planck-Scale Corrections to Friedmann Equation

Recently, Verlinde proposed that gravity is an emergent phenomenon which
originates from an entropic force. In this work, we extend Verlinde's proposal
to accommodate generalized uncertainty principles (GUP), which are suggested by
some approaches to \emph{quantum gravity} such as string theory, black hole
physics and doubly special relativity (DSR). Using Verlinde's proposal and two
known models of GUPs, we obtain modifications to Newton's law of gravitation as
well as the Friedmann equation. Our modification to the Friedmann equation
includes higher powers of the Hubble parameter which is used to obtain a
corresponding Raychaudhuri equation. Solving this equation, we obtain a leading
Planck-scale correction to Friedmann-Robertson-Walker (FRW) solutions for the
$p=\omega \rho$ equation of state.Comment: 15 pages, no figure, to appear in Central Eur.J.Phys. arXiv admin
note: text overlap with arXiv:1301.350

### Minimal Length, Friedmann Equations and Maximum Density

Inspired by Jacobson's thermodynamic approach[gr-qc/9504004], Cai et al
[hep-th/0501055,hep-th/0609128] have shown the emergence of Friedmann equations
from the first law of thermodynamics. We extend Akbar--Cai derivation
[hep-th/0609128] of Friedmann equations to accommodate a general entropy-area
law. Studying the resulted Friedmann equations using a specific entropy-area
law, which is motivated by the generalized uncertainty principle (GUP), reveals
the existence of a maximum energy density closed to Planck density. Allowing
for a general continuous pressure $p(\rho,a)$ leads to bounded curvature
invariants and a general nonsingular evolution. In this case, the maximum
energy density is reached in a finite time and there is no cosmological
evolution beyond this point which leaves the big bang singularity inaccessible
from a spacetime prospective. The existence of maximum energy density and a
general nonsingular evolution is independent of the equation of state and the
spacial curvature $k$. As an example we study the evolution of the equation of
state $p=\omega \rho$ through its phase-space diagram to show the existence of
a maximum energy which is reachable in a finite time.Comment: 15 pages, 1 figure, minor revisions, To appear in JHE

### WAP Based Email Management Application

WAP technology becomes the most appropriate and the useful tools to access the information about the different information and services anytime and anywhere. However this study identified the requirement model to manage the email by mobile device, which can be obtained easily way and flexibility to access and check the incoming emails by this service. This study introduces an application to manage
the incoming emails for those who interested in using the mobile device. However, this service will help to reduce the time for the users to check their incoming emails, especially when they are away from their work or any place can not provide the Web services. For these reasons this study carry out the manage email by mobile to obtain the appropriate solution

### Topological dyonic Taub-Bolt/NUT-AdS: Thermodynamics and first law

Motivated by the absence of Misner string in the Euclidean Taub-Bolt/NUT
solutions with flat horizons, we present a new treatment for studying the
thermodynamics of these spactimes. This treatment is based on introducing a new
charge, $N=\sigma \, n$ (where $n$ is the nut charge and $\sigma$ is some
constant) and its conjugate thermodynamic potential $\Phi_N$. Upon identifying
one of the spatial coordinates, the boundary of these solutions contains two
annulus-like surfaces in addition to the constant-r surface. For these
solutions, we show that these annuli surfaces receive electric, magnetic and
mass/energy fluxes, therefore, they have nontrivial contributions to these
conserved charges. Calculating these conserved charges we find, $Q_e =
Q^{\infty}_e-2N\Phi_m$, $Q_m =Q^{\infty}_m+2N\Phi_e$ and $\mathfrak{M}
=M-2N\Phi_N$, where $Q^{\infty}_e$, $Q^{\infty}_m$, $M$ are electric charge,
magnetic charge and mass in the $n=0$ case, while $\Phi_e$ and $\Phi_m$ are the
electric and magnetic potentials. The calculated thermodynamic quantities obey
the first law of thermodynamics while the entropy is the area of the horizon.
Furthermore, all these quantities obey Smarr's relation. We show the
consistency of these results through calculating the Hamiltonian and its
variation which reproduces the first law.Comment: 22 pages, one figur

### Dyonic Taub-NUT-AdS: Unconstraint thermodynamics and phase Structure

Here we extend the approach developed in \cite{adel_2} to study the
thermodynamics of Taub-NUT-AdS and dyonic Taub-NUT-AdS solutions. Furthermore,
we investigate in details possible phase structures of the dyonic Taub-NUT-AdS
solution. We show that the first law, Gibbs-Duhem and Smarr's relations are all
satisfied for both solutions. Our study of phase structures shows some
intriguing features, which were not reported before, among which the existence
of two distinguished critical points with a region of continuous phase
transitions in between, and the possibility of merging them into one point. To
analyze these phases we consider both canonical and mixed ensembles. The two
distinguished critical points occur for the canonical case as well as the mixed
cases with $1/2 \le \phi_e < 1$. Another interesting case is the mixed ensemble
with $\phi_e \ge 1$, where we have one critical point but the continuous phase
transition region in the $P-T$ diagram is close to the origin, in contrast with
what happens in Reissner-Nordstrom-AdS solutions and Van der Waals fluids,
i.e., the continuous phase transition happens only for low enough pressures and
temperatures!Comment: 35 pages, 18 figure

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