Pair Of Branes Research Articles

Entropy of near-extremal black holes in AdS5

We construct the microstates of near-extremal black holes in AdS_5 x S5 as gases of defects distributed in heavy BPS operators in the dual SU(N) Yang-Mills theory. These defects describe open strings on spherical D3-branes in the S5, and we show that they dominate the entropy by directly enumerating them and comparing the results with a partition sum calculation. We display new decoupling limits in which the field theory of the lightest open strings on the D-branes becomes dual to a near-horizon region of the black hole geometry. In the single-charge black hole we find evidence for an infrared duality between SU(N) Yang-Mills theories that exchanges the rank of the gauge group with an R-charge. In the two-charge case (where pairs of branes intersect on a line), the decoupled geometry includes an AdS_3 factor with a two-dimensional CFT dual. The degeneracy in this CFT accounts for the black hole entropy. In the three-charge case (where triples of branes intersect at a point), the decoupled geometry contains an AdS_2 factor. Below a certain critical mass, the two-charge system displays solutions with naked timelike singularities even though they do not violate a BPS bound. We suggest a string theoretic resolution of these singularities.

A self-tuning mechanism in (3 + p)d gravity-scalar theory

We present a new type of self-tuning mechanism for ($3+p$)d brane world models in the framework of gravity-scalar theory. This new type of self-tuning mechanism exhibits a remarkable feature. In the limit $g_s \to 0$, $g_s$ being the string coupling, the geometry of bulk spacetime remains virtually unchanged by an introduction of the Standard Model(SM)-brane, and consequently it is virtually unaffected by quantum fluctuations of SM fields with support on the SM-brane. Such a feature can be obtained by introducing Neveu-Schwarz(NS)-brane as a background brane on which our SM-brane is to be set. Indeed, field equations naturally suggest the existence of the background NS-brane. Among the given such models, of the most interest is the case with $\Lambda=0$, where $\Lambda$ represents the bulk cosmological constant. This model contains a pair of coincident branes (of the SM- and the NS-branes), one of which is a codimension-2 brane placed at the origin of 2d transverse space ($\equiv \Sigma_2$), another a codimension-1 brane placed at the edge of $\Sigma_2$. These two branes are (anti) T-duals of each other, and one of them may be identified as our SM-brane plus the background NS-brane. In the presence of the background NS-brane (and in the absence of $\Lambda$), the 2d transverse space $\Sigma_2$ becomes an orbifold $R_2 /Z_n$ with an appropriate deficit angle. But this is only possible if the ($3+p$)d Planck scale $M_{3+p}$ and the string scale $M_s$($\equiv 1/\sqrt{\alpha^{\prime}}$) are of the same order, which accords with the hierarchy assumption \cite{1,2,3} that the electroweak scale $m_{EW}$ is the only short distance scale existing in nature.

Localizing gravity on thick branes: a solution for massive KK modes of the Schrödinger equation

We generate scalar thick brane configurations in a 5D Riemannian space time which describes gravity coupled to a self-interacting scalar field. We also show that 4D gravity can be localized on a thick brane which does not necessarily respect Z2-symmetry, generalizing several previous models based on the Randall-Sundrum system and avoiding the restriction to orbifold geometries as well as the introduction of the branes in the action by hand. We begin by obtaining a smooth brane configuration that preserves 4D Poincaré invariance and violates reflection symmetry along the fifth dimension. The extra dimension can have either compact or extended topology, depending on the values of the parameters of the solution. In the non-compact case, our field configuration represents a thick brane with positive energy density centered at y = c2, whereas in the compact case we get pairs of thick branes. We recast as well the wave equations of the transverse traceless modes of the linear fluctuations of the classical solution into a Schrödinger's equation form with a volcano potential of finite bottom. We solve Schrödinger equation for the massless zero mode m2 = 0 and obtain a single bound wave function which represents a stable 4D graviton and is free of tachyonic modes with m2 < 0. We also get a continuum spectrum of Kaluza–Klein (KK) states with m2 > 0 that are suppressed at y = c2 and turn asymptotically into plane waves. We found a particular case in which the Schrödinger equation can be solved for all m2 > 0, giving us the opportunity of studying analytically the massive modes of the spectrum of KK excitations, a rare fact when considering thick brane configurations.

Connection between the Hagedorn Transision of Closed Strings and the Creation of D9-brane-&lt;D9&gt;^^^--brane pairs

Connection between the Hagedorn Transision of Closed Strings and the Creation of D9-brane-&lt;D9&gt;^^^--brane pairs

ON THE BEKENSTEIN–HAWKING ENTROPY, NONCOMMUTATIVE BRANES AND LOGARITHMIC CORRECTIONS

We extend our earlier work on the possible microscopic origin of the Bekenstein–Hawking entropy to higher-dimensional space–times. The mechanism of counting chain-like states is shown to work for space–times with event horizon wrapped by a Euclidean doublet (E1,M1)+(E2,M2) of electric–magnetic dual brane pairs of type II string-theory or M-theory. Noncommutativity on the brane worldvolume enters naturally the derivation of the Bekenstein–Hawking entropy including the correct prefactor. Moreover, a logarithmic correction with prefactor 1/2 is predicted.

Heating in brane inflation and hidden dark matter

Towards the end of brane inflation, the brane pair annihilation produces massive closedstrings. The transfer of this energy to standard model (SM) open string modes depends onwhere the SM branes and the brane annihilation are located: in the bulk, in the samethroat, or in different throats. We find that, in all cases as long as the brane annihilationand the SM branes are not both in the bulk, the transfer of energy to start the hot bigbang epoch can be efficient enough to be compatible with big bang nucleosynthesis. Thesuppression of the abundance of the graviton and its Kaluza–Klein (KK) thermalrelics follows from the warped geometry in flux compactification. This worksout even in the scenarios where a long period of tunnelling is expected. In themulti-throat scenario, we find a dynamical mechanism of selecting a long throat asthe SM throat. We establish three new dark matter candidates: KK modes withspecific angular momentum in the SM throat, those in the brane annihilationthroat, and different matters generated by KK modes tunnelled to other throats.Since the latter two couple to the visible matter sector only through gravitonmediation, they behave as hidden dark matter. Hidden dark matter has novelimplications for the dark matter coincidence problem and the high energy cosmic rays.

Localization of 4D gravity on pure geometrical thick branes

We consider the generation of thick brane configurations in a pure geometric Weyl integrable 5D spacetime which constitutes a non-Riemannian generalization of Kaluza-Klein (KK) theory. In this framework, we show how 4D gravity can be localized on a scalar thick brane which does not necessarily respect reflection symmetry, generalizing in this way several previous models based on the Randall-Sundrum (RS) system and avoiding both, the restriction to orbifold geometries and the introduction of the branes in the action by hand. We first obtain a thick brane solution that preserves 4D Poincar\'e invariance and breaks ${Z}_{2}$-symmetry along the extra dimension which, indeed, can be either compact or extended, and supplements brane solutions previously found by other authors. In the noncompact case, this field configuration represents a thick brane with positive energy density centered at $y={c}_{2}$, whereas pairs of thick branes arise in the compact case. Remarkably, the Weylian scalar curvature is nonsingular along the fifth dimension in the noncompact case, in contraposition to the RS thin brane system. We also recast the wave equations of the transverse traceless modes of the linear fluctuations of the classical background into a Schr\"odinger's equation form with a volcano potential of finite bottom in both the compact and the extended cases. We solve Schr\"odinger equation for the massless zero mode ${m}^{2}=0$ and obtain a single bound wave function which represents a stable 4D graviton. We also get a continuum gapless spectrum of KK states with ${m}^{2}&gt;0$ that are suppressed at $y={c}_{2}$ and turn asymptotically into plane waves.

Inflationary cosmology in RS-I

In this work, I intend to show a possible candidate of inflaton potential $V(\phi)$ in a scenario of a brane world defined by a pair of branes (RS-I).

DUAL BRANE PAIRS, CHAINS AND THE BEKENSTEIN–HAWKING ENTROPY

A proposal towards a microscopic understanding of the Bekenstein–Hawking entropy for D = 4 space–times is made. Euclidean D-branes wrapping the event horizon's boundary play an important role. After assuming a discretization of the Euclidean D-brane worldvolume, motivated by the worldvolume uncertainty relation, we count chainlike excitations on the worldvolume of specific dual Euclidean brane pairs. It is shown that one can thus reproduce the D = 4 Bekenstein–Hawking entropy and its logarithmic correction.

BEKENSTEIN-SPECTRUM, TEMPERATURE AND SPECIFIC HEAT OF BLACK HOLES FROM CHAINS

We study some consequences of a recently proposed description for a Schwarzschild black hole based on Euclidean [Formula: see text] brane pairs described in terms of chain-like excitations. A discrete mass-spectrum of Bekenstein-type is inferred and upon identification of the black hole mass with the chain's energy the leading corrections to both Hawking-temperature and specific heat of the black hole are obtained. The results indicate that for small black holes the evaporation process might be considerably altered.

Volume stabilization viaα′corrections in type IIB theory with fluxes

We consider the Type IIB string theory in the presence of various extra $7/\bar 7$-brane pairs compactified on a warped Calabi-Yau threefold that admits a conifold singularity. We demonstrate that the volume modulus can be stabilized perturbatively at a non-supersymmetric $AdS_4/dS_4$ vacuum by the effective potential that includes the stringy $(\alpha^\prime)^3$ correction obtained by Becker {\it et al.} together with a combination of positive tension and anomalous negative tension terms generated by the additional 7-brane-antibrane pairs.

Conformal symmetry of brane world effective actions

A simple derivation of the low-energy effective action for brane worlds is given, highlighting the role of conformal invariance. We show how to improve the effective action for a positive- and negative-tension brane pair using the AdS/CFT correspondence.

Dual brane pairs and the Bekenstein–Hawking entropy of non-Susy spacetimes

A novel approach is described towards a microscopic understanding of the Bekenstein–Hawking entropy of non-supersymmetric spacetimes—including the Schwarzschild black hole. It is based at an intermediate step on the description of the event horizon in terms of dual Euclidean brane pairs of type-II string theory or M theory. By counting specific chain structures on the brane complex, it is shown that one can reproduce the exact Schwarzschild black hole entropy plus its logarithmic correction.

Spacetime, Warped Branes, and Hidden Dimensions

Look around—how many dimensions are you aware of? Of course, you know the answer is four: three spatial dimensions and one time dimension. Four numbers are enough to locate and catalog anything that happens anywhere in the universe, for as long as the universe lasts. But why four? Where did they come from? Until fairly recently, the best minds in history had to settle for “that's just the way it is.” Then, a mere 87 years ago, Albert Einstein introduced his Theory of General Relativity, which rolls the four dimensions together into the concept of a spacetime. Suddenly the universe became tractable, malleable, an object with dynamic topology and geometry. Physicists realized that it could fluctuate, curve, and even warp in on itself to form exotic astronomical objects such as black holes. Millennia of speculation gave way to a pair of much more productive questions about the universe itself: What is its structure, and how did that structure develop? Addressing the first of those questions in this special issue on spacetime, Tegmark (p. [1427][1]) reviews the physical structure of the universe—the structure and distribution of galaxies, the formation of astronomical objects, the cosmic microwave background, gravitational lensing, and other topics—from the latest measurements made from ground-and space-based observatories, satellites, and telescopes. He also provides the experimental data that put constraints on the theoretical models proposed to describe spacetime. In tackling the second question, cosmologists go back to basics. After all, they can argue, there is no a priori reason for having four dimensions. Extra dimensions are easy to describe mathematically; why shouldn't they exist? Indeed, counterintuitive though the idea might seem, theorists have presented a slew of mathematical equations that show that extra dimensions are not only possible but necessary for a consistent description of spacetime. ![Figure][2] In the 1970s, for example, theorists working to reconcile gravity and quantum theory developed an elegant model in which the fundamental particles of our universe are viewed as excitations of a tiny subatomic species called strings. To be mathematically coherent, however, string theory needed dimensions well beyond the standard four. An obvious question arises: If these extra dimensions do exist, where are they? Randall (p. [1422][3]) provides an overview of the latest developments in string theory and extra dimensions and explores possible reasons for their being hidden from view. In particular, theory reveals that our “field of view” may be limited to a lower dimensional membrane, or brane, embedded in the higher dimensional spacetime and that collisions or interactions between branes can manifest themselves as gravitational excitations. The theory raises the humbling possibility that remnants of these collisions pave the way for the development of the structure of the universe we observe. Steinhardt elaborates on this idea in a Research Article (p. [1436][4]). His pulsating-universe model posits that pairs of branes may trigger series of big bangs as they collide again and again like sheets drying in a strong wind. If all this sounds intimidating, have no fear. News writer Charles Seife opens the section with a [nontechnical history][5] explaining how the cosmic fabric wove itself into physicists' awareness of the universe and how it can enhance your own. [1]: /lookup/doi/10.1126/science.1072184 [2]: pending:yes [3]: /lookup/doi/10.1126/science.1072567 [4]: /lookup/doi/10.1126/science.1070462 [5]: /lookup/doi/10.1126/science.296.5572.1418

Graded Chern-Simons field theory and graded topological D-branes

We discuss graded D-brane systems of the topological A model on a Calabi-Yau threefold, by means of their string field theory. We give a detailed analysis of the extended string field action, showing that it satisfies the classical master equation, and construct the associated BV system. The analysis is entirely general and it applies to any collection of D-branes (of distinct grades) wrapping the same special Lagrangian cycle, being valid in arbitrary topology. Our discussion employs a $\Z$-graded version of the covariant BV formalism, whose formulation involves the concept of {\em graded supermanifolds}. We discuss this formalism in detail and explain why $\Z$-graded supermanifolds are necessary for a correct geometric understanding of BV systems. For the particular case of graded D-brane pairs, we also give a direct construction of the master action, finding complete agreement with the abstract formalism. We analyze formation of acyclic composites and show that, under certain topological assumptions,all states resulting from the condensation process of a pair of branes with grades differing by one unit are BRST trivial and thus the composite can be viewed as a closed string vacuum. We prove that there are {\em six} types of pairs which must be viewed as generally inequivalent. This contradicts the assumption that `brane-antibrane' systems exhaust the nontrivial dynamics of topological A-branes with the same geometric support.

Forces between stable non-BPS branes

As a step toward constructing realistic brane world models in string theory, we consider the interactions of a pair of non-BPS branes. We construct a dyonic generalization of the non-BPS branes first constructed by Bergman, Gaberdiel and Sen as orbifolds of D-branes on $T^4/\BZ_2$. The force between a dyonic brane and an electric brane is computed and is found to vanish at a nontrivial critical separation. This equilibrium point is unstable. For smaller separations the branes coalesce to form a composite dyonic state, while for larger separations the branes run off to infinity. We suggest generalizations that will lead to potentials with stable local minima.

The Kaluza Klein Melvin solution in M-theory

We study some aspects of the Kaluza-Klein Melvin solution in M-theory. The associated magnetic field has a maximal critical value $B=\pm 1/R$ where $R$ is the radius of the compactification circle. It is argued that the Melvin background of type IIA with magnetic field $B$ and of type 0A with magnetic field $B'=B-1/R$ are equivalent. Evidence for this conjecture is provided using a further circle compactification and a `9-11' flip. We show that partition functions of nine-dimensional type IIA strings and of a $(-1)^F\sigma_{1/2}$ type IIA orbifold both with NS-NS Melvin fluxtubes are related by such shift of the magnetic field. Then the instabilities of both IIA and 0A Melvin solutions are analyzed. For each theory there is an instanton associated to the decay of spacetime. In the IIA case the decay mode is associated to the nucleation of $D6/D\bar{6}$-brane pairs, while in the 0A case spacetime decays through Witten's bubble production.

Branes and fluxes in D=5 Calabi–Yau compactifications of M-theory

We discuss Poincaré three-brane solutions in D=5 M-theory compactifications on Calabi–Yau (CY) threefolds with G-fluxes. We show that the vector moduli freeze at an attractor point. In the case with background flux only, the spacetime geometry contains a zero volume singularity with the three-brane and the CY space shrinking simultaneously to a point. This problem can be avoided by including explicit three-brane sources. We consider two cases in detail: a single brane and, when the transverse dimension is compactified on a circle, a pair of branes with opposite tensions.

Brane-antibrane constructions

In type II string theories, we examine intersecting brane constructions containing brane-antibrane pairs suspended between 5-branes, and more general non-BPS constructions. The tree-level spectra are obtained in each case. We identify various models with distinct physics: parallel brane-antibrane pairs, adjacent pairs, non-adjacent pairs, and configurations which break all supersymmetry even though any pair of branes preserves some supersymmetry. In each case we examine the possible decay modes. Some of these configurations turn out to be tachyon-free, stable non-BPS states. We use T-duality to map some of our brane constructions to brane-antibrane pairs at ALE singularities. This enables us to explicitly derive the spectra by the analogue of the quiver construction, and to compute the sign of the brane-antibrane force in each case.

Holograms of branes in the bulk and acceleration terms in SYM effective action

If the AdS/CFT correspondence is valid in the Coulomb branch, the potential between waves on a pair of test branes in the bulk should be reproduced by the relevant Yang-Mills theory effective action on the boundary. Earlier work has provided evidence for this in the case of constant gauge field brane waves. In this paper we provide concrete evidence for an earlier proposal that the effects of exchange of supergravity modes with nonzero momentum in the brane directions are encoded in certain terms involving derivatives of the field strength in the gauge theory effective action. We explicitly calculate the force quadratic in the field strengths coming from the exchange of nonzero momentum two form fields between two 3-branes in AdS5 × S5 to lowest nontrivial order in the momentum. We show that this is exactly the same as that between the branes living in flat space. The result is in agreement with the gauge theory effective action and consistent with the non-renormalization property of this term. We comment on the relationship of other ``acceleration'' terms in the SYM effective action with quantities in supergravity.