281 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 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 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 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
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 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 . As an example we study the evolution of the equation of
state 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, (where is the nut charge and is some
constant) and its conjugate thermodynamic potential . 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, , and , where , , are electric charge,
magnetic charge and mass in the case, while and 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
The armament of the Almoravid army
El estado almorávide se sustentaba en
elementos bélicos y militares. El ejército era la base fundamental de su existencia. Yusuf Ibn
Tašufin, el fundador del gran estado almorávide, procuró organizar el ejército almorávide y
proveerlo del equipamiento y el armamento necesario, hasta que se convirtió en uno de los ejércitos
más poderosso del momento, al sustituir el armamento sencillo propio de los combates de la vida
beduina por un tipo de armamento que le permitió superar a sus enemigos en el Magreb, al-Andalus
y los reinos cristianos. Este tipo de armamento incluía armas ligeras, pesadas, económicas,
personales y defensivas (fortificaciones). El presente estudio detalla algunas de esas armas,
incluyendo armamento de tipo químico, que se utilizaba dependiendo del tipo de combate o batalla
al que se enfrentaban.The Almoravid state was based on war and
military elements. In fact, the army was considered a crucial element. Yusuf Ibn Tashufin, the
founder of the great Almoravid state, sought to organize the Almoravid army and provide the
necessary equipment and weapons so it became one of the most powerful armies of the time, by
menas of replacing the simple type of weapons used in Bedouin life style by new types of weapons
that allowed them to overcome their enemies in the Maghrib, Al-andalus and the Christian
kingdoms. These weapons include light, heavy, economic, personal and defensive weapons
(fortifications). This paper provide further details about some of these weapons, including weapons
of chemical nautre, which were used in some batles they faced
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