119287730
Fermi surfaces and analytic Green’s functions from conformal gravity
A bstractWe construct T2-symmetric charged AdS black holes in conformal gravity. The most general solution up to an overall conformal factor contains three non-trivial parameters: the mass, electric charge and a quantity that can be identified as the massive spin-2 hair. We study the Dirac equation for the charged massless spinor in this background. The equation can be solved in terms of the general Heun’s function for generic frequency ω and wave number k. This allows us to obtain the analytic Green’s function G(ω, k) for both extremal and non-extremal black holes. For some special choice of back hole parameters, we find that the Green’s function reduces to simpler hypergeometric or confluent hypergeometric functions. We study the Fermi surfaces associated with the poles of the Green’s function with vanishing ω. We find examples where the Fermi surfaces for non-Fermi liquids as well as the characteristic Fermi ones can arise. We illustrate the non-trivial differences in the Green’s function and Fermi surfaces between the extremal and non-extremal black holes.
119113707
f(R) gravities, Killing spinor equations, “BPS” domain walls and cosmology
A bstractWe derive the condition on f(R) gravities that admit Killing spinor equations and construct explicit such examples. The Killing spinor equations can be used to reduce the fourth-order differential equations of motion to the first order for both the domain wall and FLRW cosmological solutions. We obtain exact “BPS” domain walls that describe the smooth Randall-Sundrum II, AdS wormholes and the RG flow from IR to UV. We also obtain exact smooth cosmological solutions that describe the evolution from an inflationary starting point with a larger cosmological constant to an ever-expanding universe with a smaller cosmological constant. In addition, We find exact smooth solutions of pre-big bang models, bouncing or crunching universes. An important feature is that the scalar curvature R of all these metrics is varying rather than a constant. Another intriguing feature is that there are two different f(R) gravities that give rise to the same “BPS” solution. We also study linearized f(R) gravities in (A)dS vacua.
119247810
Killing spinors for the bosonic string and Kaluza–Klein theory with scalar potentials
The paper consists mainly of two parts. In the first part, we obtain well-defined Killing spinor equations for the low-energy effective action of the bosonic string with the conformal anomaly term. We show that the conformal anomaly term is the only scalar potential that one can add into the action that is consistent with the Killing spinor equations. In the second part, we demonstrate that Kaluza–Klein theory can be gauged so that the Killing spinors are charged under the Kaluza–Klein vector. This gauging process generates a scalar potential with a maximum that gives rise to an AdS spacetime. We also construct solutions of these theories.
119264434
f (R) Theories of supergravities and pseudo-supergravities
A bstractWe present f (R) theories of ten-dimensional supergravities, up to and including the quadratic order in fermion fields in action. They are obtained by performing the conformal scaling on the usual supergravities to the f (R) frame in which the dilaton becomes an auxiliary field and can be integrated out. The f (R) frame coincides with that of M-theory, D2-branes or NS-NS 5-branes. We study various BPS p-brane solutions and their near-horizon AdS × sphere geometries in the context of the f (R) theories. We find that new solutions emerge with global structures that do not exist in the corresponding solutions of the original supergravity description. In lower dimensions, We construct the f (R) theory of $\mathcal{N} = 2$, D = 5 gauged supergravity with a vector multiplet, and that for the four-dimensional U(1)4 gauged theory with three vector fields set equal. We find that some previously-known BPS singular “superstars” become wormholes in the f (R) theories. We also construct a large class of f (R) (gauged) pseudo-supergravities. In addition we show that the breathing mode in the Kaluza-Klein reduction of Gauss-Bonnet gravity on S1 is an auxiliary field and can be integrated out.
118627339
$5D$ Solutions to $\Lambda$CDM Universe Derived from Global Brane Model
An exact solution of brane universe is studied and the result indicates that Friedmann equations on the brane are modified with an extra term. This term can play the role of dark energy and make the universe accelerate. In order to derive the $\Lambda$CDM Universe from this global brane model, the new solutions are obtained to describe the $5D$ manifold.
118929827
FIVE-DIMENSIONAL COSMOLOGICAL SCALING SOLUTION
A five-dimensional Ricci-flat cosmological solution is studied by assuming that the induced 4D matter contains two components: the usual fluid for dark matter as well as baryons and a scalar field with an exponential potential for dark energy. With use of the phase-plane analysis it is shown that there exist two late-time attractors one of which corresponds to a universe dominated by the scalar field alone and the other is a scaling solution in which the energy density of the scalar field remains proportional to that of the dark matter. It is furthermore shown that for this 5D scaling solution the universe expands with the same rate as in the 4D FRW models and not relies on which 4D hypersurface the universe is located in the 5D manifold.
17322710
Quantum hair, instantons, and black hole thermodynamics: some new results
Abstract We present results obtained by a consideration of the non-classical energy-momentum tensor associated with Euclidean instantons outside the event horizon of black holes. We demonstrate here how this allows for an analytic estimate to be made of the effect of discrete quantum hair on the temperature of the black hole, in which the role of violations of the weak energy condition associated with instantons is made explicit, and in which the previous results of Coleman, Preskill, and Wilczek are extended. Last, we demonstrate how the existence of a non-classical electric field outside the event horizon of black holes, uncovered by these authors, can be identified with a well-known effect in the Abelian Higgs mode] in two dimensions. In this case, there is a one-to-one connection between the discrete charge of a black hole and a topological phase in two dimensions.
119170407
The real solution to scalar field equation in 5D black string space
After the nontrivial quantum parameters Ωn and quantum potentials Vn obtained in our previous research, the circumstance of a real scalar wave in the bulk is studied with the similar method of Brevik and Simonsen (Gen. Rel. Grav. 33:1839, 2001). The equation of a massless scalar field is solved numerically under the boundary conditions near the inner horizon re and the outer horizon rc. Unlike the usual wave function Ψωl in 4D, quantum number n introduces a new functions Ψωln, whose potentials are higher and wider with bigger n. Using the tangent approximation, a full boundary value problem about the Schrödinger-like equation is solved. With a convenient replacement of the 5D continuous potential by square barrier, the reflection and transmission coefficients are obtained. If extra dimension does exist and is visible at the neighborhood of black holes, the unique wave function Ψωln may say something to it.
117523806
Reconstruction of a Deceleration Parameter from the Latest Type Ia Supernovae Gold Dataset
Recent observations of High redshift Type Ia Supernova indicate that our universe is undergoing accelerated ex-pansion which is one of the biggest challenges in present cosmological research, now [1, 2, 3, 4, 5, 6]. Meanwhile, thissuggestion is strongly conﬁrmed by the observations from WMAP [7, 8, 9, 10] and Large Scale Structure survey [11].To understand the late-time accelerated expansion of the universe, a large part of models are proposed by assumingthe existence of an extra energy component with negative pressure and dominated at late time pushing the universeto accelerated expansion. In principle, a natural candidate for dark energy could be a small cosmological constantΛ which has the constant equation of state (EOS) w