14992212
CORRESPONDENCE BETWEEN 5D RICCI-FLAT COSMOLOGICAL MODELS AND QUINTESSENCE DARK ENERGY MODELS
We study the accelerating expansion and the induced dark energy of the 5D Ricci-flat universe which is characterized by having a big bounce as opposed to a big bang. We show that the arbitrary function μ(t) contained in the 5D solutions can be rewritten in terms of the redshift z as a new arbitrary function f(z), and we find that there is a correspondence between this f(z) and the potential V(ϕ) of the 4D quintessence models. Using this correspondence, the arbitrary function f(z) and the 5D solution could be specified for a given form of the potential V(ϕ).
123723006
PARTICLE MASSES IN KALUZA–KLEIN–GORDON THEORY AND THE REALITY OF EXTRA DIMENSIONS
To see how the effective 4-D mass of a particle is affected by the geometry of an ND space, we take the Klein–Gordon equation in 5-D and evaluate it in 4-D using two exact solutions of 5-D Kaluza–Klein theory. The mass (squared) turns out to be complex if the theory is independent of the extra coordinate, but can be made real if the wave function depends on an extra dimension which is physical. These results have significant implications for 10-D superstring theory.
53459258
Reconstruction of Five-Dimensional Bounce Cosmological Models from Deceleration Factor
In this paper, we consider a class of five-dimensional Ricci-flat vacuum solutions, which contain two arbitrary functions μ(t) and ν(t). It is shown that μ(t) can be rewritten as a new arbitrary function f(z) in terms of redshift z and the f(z) can be determined by choosing particular deceleration parameters q(z) which gives early deceleration and late time acceleration. In this way, the 5D cosmological model can be reconstructed and the evolution of the universe can be determined.
49526339
Brane Formation and Cosmological Constraint on the Number of Extra Dimensions
Special relativity is generalized to extra dimensions and quantized energy levels of particles are obtained. By calculating the probability of particles' motion in extra dimensions at high temperature of the early universe, it is proposed that the branes may have not existed since the very beginning of the universe, but formed later. Meanwhile, before the formation, particles of the universe may have filled in the whole bulk, not just on the branes. This scenario differs from that in the standard big bang cosmology in which all particles are assumed to be in the 4D spacetime. So, in brane models, whether our universe began from a 4D big bang singularity is questionable. A cosmological constraint on the number of extra dimensions is also given which favors N ≥ 7.
14287684
Correspondence Between DGP Brane Cosmology and $5D$ Ricci-flat Cosmology
We discuss the correspondence between the DGP brane cosmology and 5D Ricci-flat cosmology by letting their metrics equal each other. By this correspondence, a specific geometrical property of the arbitrary integral constant I in DGP metric is given and it is related to the curvature of 5D bulk. At the same time, the relation of arbitrary functions μ and ν in a class of Ricci-flat solutions is obtained from DGP brane metric.
118482632
The Numerical Solution of Scalar Field for Nariai Case in 5D Ricci-flat SdS Black String Space with Polynomial Approximation
As one exact candidate of the higher dimensional black hole, the 5D Ricci-flat Schwarzschild-de Sitter black string space presents something interesting. In this paper, we give a numerical solution to the real scalar field around the Nariai black hole by the polynomial approximation. Unlike the previous tangent approximation, this fitting function makes a perfect match in the leading intermediate region and gives a good description near both the event and the cosmological horizons. We can read from our results that the wave is close to a harmonic one with the tortoise coordinate. Furthermore, with the actual radial coordinate the waves pile up almost equally near the both horizons.
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.
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.
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.
1499155
Structure and mutagenic conversion of E1 dehydrase: at the crossroads of dehydration, amino transfer, and epimerization.
Pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP) are highly versatile coenzymes whose importance is well recognized. The capability of PLP/PMP-dependent enzymes to catalyze a diverse array of chemical reactions is attributed to fine-tuning of the cofactor-substrate interactions in the active site. CDP-6-deoxy-L-threo-D-glycero-4-hexulose 3-dehydrase (E1), along with its reductase (E3), catalyzes the C-3 deoxygenation of CDP-4-keto-6-deoxy-D-glucose to form the dehydrated product, CDP-4-keto-3,6-dideoxy- d-glucose, in the ascarylose biosynthetic pathway. This product is the progenitor to most 3,6-dideoxyhexoses, which are the major antigenic determinants of many Gram-negative pathogens. The dimeric [2Fe-2S] protein, E 1, cloned from Yersinia pseudotuberculosis, is the only known enzyme whose catalysis involves the direct participation of PMP in one-electron redox chemistry. E1 also contains an unusual [2Fe-2S] cluster with a previously unknown binding motif (C-X 57-C-X 1-C-X 7-C). Herein we report the first X-ray crystal structure of E1, which exhibits an aspartate aminotransferase (AAT) fold. A comparison of the E1 active site architecture with homologous structures uncovers residues critical for the dehydration versus transamination activity. Site-directed mutagenesis of four E1 residues, D194H, Y217H, H220K, and F345H, converted E 1 from a PMP-dependent dehydrase to a PLP/glutamate-dependent aminotransferase. The E1 quadruple mutant, having been conferred this altered enzyme activity, can transaminate the natural substrate to CDP-4,6-dideoxy-4-amino-D-galactose without E3. Taken together, these results provide the molecular basis of the functional switch of E1 toward dehydration, epimerization, and transamination. The insights gained from these studies can be used for the development of inhibitors of disease-relevant PLP/PMP-dependent enzymes.
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.