[en] In this paper we analyze the problem of fermion creation as a dynamical Casimir effect inside a three dimensional sphere. We present an appropriate wave function which satisfies the Dirac equation in this geometry with MIT bag model boundary condition. We consider the radius of the sphere to have dynamics and introduce the time evolution of the quantized field by expanding it over the instantaneous basis. We explain how we can obtain the average number of particles created. In this regard we find the Bogoliubov coefficients. We consider an oscillation and determine the coupling conditions between different modes that can be satisfied depending on the cavity's spectrum. Assuming the parametric resonance case we obtain an expression for the mean number of created fermions in each mode of an oscillation.

[en] In this paper, we examine the validity of the first law of inner mechanics of black holes in Generalized Minimal Massive Gravity. We consider BTZ and spacelike warped black holes and show that the first law of inner mechanics is valid for given black holes in Generalized Minimal Massive Gravity. As we expect, due to the presence of the Lorentz Chern-Simons term in Lagrangian of considered model, the product of the entropies of the inner and outer horizons depends on the mass as it happens in Topologically Massive Gravity. (orig.)

[en] In this paper we provide the first non-trivial evidence for universality of the entropy formula $4\mathrm{\pi <!--\; ??\; -->}{J}_0^{+}{J}_0^{-<!--\; ???\; -->}$ beyond pure Einstein gravity in 4-dimensions. We consider the Einstein-Maxwell theory in the presence of cosmological constant, then write near horizon metric of the Kerr-Newman (A)dS black hole in the Gaussian null coordinate system. We consider near horizon fall-off conditions for metric and $U(1)$ gauge field. We find asymptotic combined symmetry generator, consists of diffeomorphism and $U(1)$ gauge transformation, so that it preserves fall-off conditions. Consequently, we find supertranslation, supperrotation and multiple-charge modes and then we show that the entropy formula is held for the Kerr-Newman (A)dS black hole. Supperrotation modes suffer from a problem. By introducing new combined symmetry generator, we cure that problem.

[en] Highlights: • We considered a non-minimal coupling inflationary model in the context of the constant-roll idea which was investigated by the first-order formalism. • We attempted to find the hidden symmetries behind the model by the Lie symmetry method. • We supplied this aim using the symmetry features of the Heun function. • We showed that the hidden symmetries of the nonminimal constant-roll inflation in the cases of power-law and exponential couplings are characterized as a generalized form of $sl(2,R)$ and $su(1,1)$ algebra, respectively. In the present work, we consider the non-minimal coupling inflationary model in the context of the constant-roll idea which is investigated by the first-order formalism. We attempt to find the hidden symmetries behind the model by the Lie symmetry method. We supply this aim by using the symmetry features of the Heun function instead of Killing vector approach. We show that the hidden symmetries of the non-minimal constant-roll inflation in the cases of power-law and exponential couplings are characterized as a generalized form of $sl(2,R)$ and $su(1,1)$ algebra,

[en] Constant-roll warm inflation is introduced in this work. A novel approach to finding an exact solution for Friedman equations in the constant-roll framework is presented for cold inflation and is extended to warm inflation with the constant dissipative parameter Q=Γ/3H. The evolution of the primordial inhomogeneities of a scalar field in a thermal bath is also studied. The $1\mathrm{\sigma <!--\; ??\; -->}$ consistency between the theoretical predictions of the model and observational constraints has been proven for a range of $Q$ and β=−φ̈/(3Hφ) (constant rate of inflaton roll). In addition, we briefly investigate the possible enhancement of super-horizon perturbations beyond the slow-roll approximation.

[en] Recently, Padmanabhan (arXiv:1206.4916 [hepth]) discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The main question arising is: what is the origin of this inequality between the surface degrees of freedom and the bulk degrees of freedom? We answer this question in M-theory. In our model, first M0-branes are compactified on one circle and N D0-branes are created. Then N D0-branes join each other, grow, and form one D5-branes. Next, the D5-brane is compactified on two circles and our universe's D3-brane, two D1-branes and some extra energies are produced. After that, one of the D1-branes, which is closer to the universe's brane, gives its energy into it, and this leads to an increase in the difference between the numbers of degrees of freedom and the occurring inflation era. With the disappearance of this D1-brane, the number of degrees of freedom of boundary surface and bulk region become equal and inflation ends. At this stage, extra energies that are produced due to the compactification cause an expansion of the universe and deceleration epoch. Finally, another D1-brane dissolves in our universe's brane, leads to an inequality between degrees of freedom, and there occurs a new phase of acceleration. (orig.)

[en] Recently, Padmanabhan discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The main question arising is: what is the origin of this inequality between the surface degrees of freedom and the bulk degrees of freedom? We answer this question in M-theory. In our model, first M0-branes are compactified on one circle and ND0-branes are created. Then ND0-branes join each other, grow, and form one D5-branes. Next, the D5-brane is compactified on two circles and our universe’s D3-brane, two D1-branes and some extra energies are produced. After that, one of the D1-branes, which is closer to the universe’s brane, gives its energy into it, and this leads to an increase in the difference between the numbers of degrees of freedom and the occurring inflation era. With the disappearance of this D1-brane, the number of degrees of freedom of boundary surface and bulk region become equal and inflation ends. At this stage, extra energies that are produced due to the compactification cause an expansion of the universe and deceleration epoch. Finally, another D1-brane dissolves in our universe’s brane, leads to an inequality between degrees of freedom, and there occurs a new phase of acceleration

[en] In this paper, we analyze the holographic cosmology using a M2–M5 brane configuration. In this configuration, a M2-brane will be placed in between a M5-brane and an anti-M5-brane. The M2-brane will act as a channel for energy to flow from an anti-M5-brane to a M5-brane, and this will increase the degrees of freedom on the M5-brane causing inflation. The inflation will end when the M5-brane and anti-M5-brane get separated. However, at a later stage the distance between the M5-brane and the anti-M5-bran can reduce and this will cause the formation of tachyonic states. These tachyonic states will again open a bridge between the M5-branes and the anti-M5-branes, which will cause further acceleration of the universe.

[en] We give a detailed review of construction of conserved quantities in extended theories of gravity for asymptotically maximally symmetric spacetimes and carry out explicit computations for various solutions. Our construction is based on the Killing charge method, and a proper discussion of the conserved charges of extended gravity theories with this method requires studying the corresponding charges in Einstein’s theory with or without a cosmological constant. Hence we study the ADM charges (in the asymptotically flat case but in generic viable coordinates), the AD charges (in generic Einstein spaces, including the anti-de Sitter spacetimes) and the ADT charges in anti-de Sitter spacetimes. We also discuss the conformal properties and the behavior of these charges under large gauge transformations as well as the linearization instability issue which explains the vanishing charge problem for some particular extended theories. We devote a long discussion to the quasi-local and off-shell generalization of conserved charges in the 2+1 dimensional Chern–Simons like theories and suggest their possible relevance to the entropy of black holes.

[en] We propose a cosmological model that unifies inflation, deceleration and acceleration phases of expansion history by a BIonic system. At the beginning, there are k black fundamental strings that transited to the BIon configuration at a given corresponding point. Here, two coupled universes, brane and antibrane, are created interacting each other through a wormhole and inflate. With decreasing temperature, the energy of this wormhole flows into the universe branes and leads to inflation. After a short time, the wormhole evaporates, the inflation ends and a deceleration epoch starts. By approaching the brane and antibrane universes together, a tachyon is born, grows and causes the creation of a new wormhole. At this time, the brane and antibrane universes result connected again and the late-time acceleration era of the universe begins. We compare our model with previous unified phantom models and observational data obtaining some cosmological parameters like temperature in terms of time. We also find that deceleration parameter is negative during inflation and late-time acceleration epochs, while it is positive during the deceleration era. This means that the model is consistent, in principle, with cosmological observations