We study type IIA superstring theory on a PP-wave background with 24 supercharges. This model can exactly be solved and then quantized. The open string in this PP-wave background is also studied. We observe that the theory has supersymmetric Dp-branes for p = 2, 4, 6, 8.
By placing a collection of membranes in 11 dimensional background supergravity six form field and considering the non-linear action of multiple membranes we obtain the potential for transverse scalar fields of membranes at leading order and study some possible vacuum configurations. We find that the system has a stable vacuum in which is a formation of membranes into fuzzy three sphere.
Considering the cubic theory of gravity which has been constructed in [6], we study the existence of Lifshitz and hyper scaling violating Lifshitz solutions. We firstly extend the black hole solution of [6] and find that such extended solutions are valid for any value of dynamical exponent z.Next, we examine the existence of the AdS black hole solution with nonzero hyperscaling-violating exponent θ and general dynamical exponent z. We find that the solutions do exist only for θ = 0, 3 in 4 dimension and θ = 0, 4 in 5 dimension. In particular, when θ = 3(4) in 4(5) dimension, we have Lifshitz and Schwarzschild-AdS black hole solution solution for z = {0, 1}.
In this paper, we study the generation of a large scale magnetic field with amplitude of order µG in an inflationary model which has been introduced in hep/th 0310221. This inflationary model based on existence of a speed limit for inflaton field. Generating a mass for inflaton at scale above the φ IR , breaks the conformal triviality of the Maxwell equation and causes to originate a magnetic field during the inflation. The amplitude strongly depends on the details of reheating stage and also depends on the e-foldings parameter N. We find the amplitude of the primordial magnetic field at decoupling time in this inflationary background using late time behavior of the theory.
By using the recently proposed prescription [1] for obtaining the M 5 brane action from multiple M 2 branes action in BLG theory, we examine such transition when 11 Dimensional background antisymmetric fluxes couple to the M 2 brane world volume. Such couplings was suggested in [2] where it was used the fact that various fields in BLG theory are valued in a Lie 3-algebra. We argue that this action and promoting it by Nambu-Poisson bracket gives the expected coupling of fluxes with M 5 brane at least at weak coupling limit. We also study some other aspects of the action for example, the gauge invariance of the theory.1 Ganjali@theory.ipm.ac.ir 2 Recently, a non linear theory for multiple M 2 branes was proposed in [8].
Recently, it was shown that half BPS Supergravity solution of theories with SU(2|4) symmetry algebra is given uniformly by determining a single function which obeys three dimensional continuous Toda equation. In this paper, we study the scale invariant solution of Toda equation. Our motivation is that some solutions of half BPS sector of IIB supergravity, as one excepts from the fermion description of the theory, are scale invariant. By defining two auxiliary functions we prove that such solutions of Toda equation obey cubic algebraic equation. We obtain some simpl solutions of Toda equation specially, we observe that the PP-wave solution can be written in this fashion.
In this paper, we study the field dynamics in Tortoise coordinate where the equation of motion of a scalar can be written as Schrodinger-like form. We obtain a general form for effective potential by finding the Schrodinger equation for scalar and spinor fields and study its global behavior in some black hole backgrounds in three dimension such as BTZ black holes, new type black holes and black holes with no horizon.Especially, we study the asymptotic behavior of potential at infinity, horizons and origin and find that its asymptotic in BTZ and new type solution is completely different from that of vanishing horizon solution. In fact, potential for vanishing horizon goes to a fixed quantity at infinity, while in BTZ and new type black hole we have an infinite barrier.
In this note, we examine the scattering of two identical fermions in theories where fermionic fields minimally coupled to higher derivative gravity. In particular, we consider the extension of general relativity with R 2 corrections or non-local terms. We expand the action of fermions around the flat space background and obtain two fermion-one graviton vertex. Then, by considering the scattering amplitude of two fermions, we calculate the non-relativistic limit and that obtain the potential for two fermion-fermion interaction which would be the usual Newtonian potential corrected with a Yukawa-like term. At the end, we briefly discuss the astronomical effects of such Yukawa-like potential by computing the gravitational pressure of a spherical star and use it for a white dwarf to obtain quantum corrections of Chandrasekhar radius.
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