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Mirjam Cvetic

Publications and source records attributed to Mirjam Cvetic.

At least 127 records · Page 7Linked to original sources
arXiv1996

Entropy of Non-Extreme Charged Rotating Black Holes in String Theory

We give the explicit expression for four-dimensional rotating charged black hole solutions of N=4 (or N=8) superstring vacua, parameterized by the ADM mass, four charges (two electric and two magnetic charges, each arising from a different U(1) gauge factors), and the angular momentum (as well as the asymptotic values of four toroidal moduli of two-torus and the dilaton-axion field). The explicit form of the thermodynamic entropy is parameterized in a suggestive way as a sum of the product of the `left-moving' and the `right-moving' terms, which may have an interpretation in terms of the microscopic degrees of freedom of the corresponding D-brane configuration. We also give an analogous parameterization of the thermodynamic entropy for the recently obtained five-dimensional rotating charged black holes parameterized by the ADM mass, three U(1) charges and two rotational parameters (as well as the asymptotic values of one toroidal modulus and the dilaton).

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arXiv1996

Near-BPS-Saturated Rotating Electrically Charged Black Holes as String States

We construct generating solutions for general D-dimensional ($4 \le D \le 9$) rotating, electrically charged, black holes in the effective action of toroidally compactified heterotic (or Type IIA) string. The generating solution is parameterized by the ADM mass, two electric charges and $[{D-1}\over 2]$ angular momenta (as well as the asymptotic values of one toroidal modulus and the dilaton field). For $D \ge 6$, those are generating solutions for {\it general} black holes in toroidally compactified heterotic (or type IIA) string. Since in the BPS-limit (extreme limit) these solutions have singular horizons or naked singularities, we address the near extreme solutions with all the angular momenta small enough. In this limit, the thermodynamic entropy can be cast in a suggestive form, which has a qualitative interpretation as microscopic entropy of (near)-BPS-saturated charged string states of toroidally compactified heterotic string, whose target-space angular momenta are identified as $[{{D-1}\over 2}]$ U(1) left-moving world-sheet currents.

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arXiv1996

General Static Spherically Symmetric Black Holes of Heterotic String on a Six Torus

We present the most general static, spherically symmetric solutions of heterotic string compactified on a six-torus that conforms to the conjectured ``no-hair theorem'', by performing a subset of O(8,24) transformations, i.e., symmetry transformations of the effective three-dimensional action for stationary solutions, on the Schwarzschild solution. The explicit form of the generating solution is determined by six $SO(1,1)\subset O(8,24)$ boosts, with the zero Taub-NUT charge constraint imposing one constraint among two boost parameters. The non-nontrivial scalar fields are the axion-dilaton field and the moduli of the two-torus. The general solution, parameterized by {\it unconstrained} 28 magnetic and 28 electric charges and the ADM mass compatible with the Bogomol'nyi bound, is obtained by imposing on the generating solution $[SO(6)\times SO(22)]/[SO(4)\times SO(20)] \subset O(6,22)$ (T-duality) transformation and $SO(2)\subset SL(2,R)$ (S-duality) transformation, which do not affect the four-dimensional space-time. Depending on the range of boost parameters, the non-extreme solutions have the space-time of either Schwarzschild or Reissner-Nordstr\" om black hole, while extreme ones have either null (or naked) singularity, or the space-time of extreme Reissner-Nordstr\" om black hole.

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arXiv1996

Supergravity Domain Walls

We review the status of domain walls in $N=1$ supergravity theories for both the vacuum domain walls as well as dilatonic domain walls. We concentrate on a systematic analysis of the nature of the space-time in such domain wall backgrounds and the special role that supersymmetry is playing in determining the nature of such configurations.

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arXiv1996

Massless BPS-Saturated States on the Two-Torus Moduli Sub-Space of Heterotic String

Within a four-dimensional, toroidally compactified heterotic string, we identify (quantized) charge vectors of electrically charged BPS-saturated states (along with the tower of SL(2,Z) related dyonic states), which preserve 1/2 of N=4 supersymmetry and become massless along the hyper-surfaces of enhanced gauge symmetry of the two-torus moduli sub-space. In addition, we identify charge vectors of the dyonic BPS-saturated states (along with the tower of SL(2,Z) related states), which preserve 1/4 of N=4 supersymmetry, and become massless at two points with the maximal gauge symmetry enhancement.

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arXiv1996

New Gauge Bosons from String Models

We address the mass ranges of new neutral gauge bosons and constraints on the accompanying exotic particles as predicted by a class of superstring models. Under certain assumptions about the supersymmetry breaking parameters we show that breaking of an additional U(1)' symmetry is radiative when the appropriate Yukawa couplings of exotic particles are of order one, analogous to the radiative breaking of the electro-weak symmetry in the supersymmetric standard model due to the large top-quark Yukawa coupling. Such large Yukawa couplings occur for a large class of string models. The Z' and exotic masses are either of O(M_Z), or of a scale intermediate between the string and electro-weak scales. In the former case, M_Z'=O(1 TeV) may be achievable without excessive fine tuning, and is within future experimental reach. (This paper is a summary, with a more phenomenological emphasis and additional discussion, of the results in our earlier article "Implications of Abelian Extended Gauge Structures from String Models", hep-ph/9511378.)

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arXiv1995

Implications of Abelian Extended Gauge Structures From String Models

Within a class of superstring vacua which have an additional non-anomalous $U(1)'$ gauge factor, we address the scale of the $U(1)'$ symmetry breaking and constraints on the exotic particle content and their masses. We also show that an extra gauge $U(1)'$ provides a new mechanism for generating a naturally small effective $μ$ term. In general, existing models are not consistent with all phenomenological constraints; however, they do provide a testing ground to address the above issues, yielding a set of concrete scenarios. Under the assumptions that the spontaneous $U(1)'$ breaking takes place in the observable sector and that the supersymmetry breaking scalar mass square terms are positive at the string scale, the breaking of $U(1)'$ symmetry is radiative. It can take place when the appropriate Yukawa couplings of exotic particles are of order one, which occurs for $Z_2\times Z_2$ fermionic orbifold constructions at symmetric points of moduli space. The $Z'$ mass is either of ${\cal O}(M_Z)$, when the symmetry breaking is due to a single standard model singlet, or is of a scale intermediate between the string and electro-weak scales, determined by the radiative corrections (or by competing non-renormalizable operators), when the breaking is due to two or more mirror-like singlets. In the former case, the $M_{Z'}/M_Z$ hierarchy achievable without excessive fine tuning is within future experimental reach.

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arXiv1995

Dyonic BPS Saturated Black Holes of Heterotic String on a Six-Torus

Within effective heterotic superstring theory compactified on a six-torus we derive minimum energy (supersymmetric), static, spherically symmetric solutions, which are manifestly invariant under the target space $O(6,22)$ and the strong-weak coupling $SL(2)$ duality symmetries with 28 electric and 28 magnetic charges subject to one constraint. The class of solutions with a constant axion corresponds to dyonic configurations subject to two charge constraints, with purely electric [or purely magnetic] and dyonic configurations preserving ${1\over 2}$ and ${1\over 4}$ of $N=4$ supersymmetry, respectively. General dyonic configurations in this class have a space-time of extreme Reissner-Nordstr\" om black holes while configurations with more constrained charges have a null or a naked singularity.

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arXiv1995

All the Four Dimensional Static, Spherically Symmetric Solutions of Abelian Kaluza-Klein Theory

We present the explicit form for all the four dimensional, static, spherically symmetric solutions in $(4+n)$-d Abelian Kaluza-Klein theory by performing a subset of $SO(2,n)$ transformations corresponding to four $SO(1,1)$ boosts on the Schwarzschild solution, supplemented by $SO(n)/SO(n-2)$ transformations. The solutions are parameterized by the mass $M$, Taub-Nut charge $a$, $n$ electric $\vec{\cal Q}$ and $n$ magnetic $\vec{\cal P}$ charges. Non-extreme black holes (with zero Taub-NUT charge) have either the Reissner-Nordstr\" om or Schwarzschild global space-time. Supersymmetric extreme black holes have a null or naked singularity, while non-supersymmetric extreme ones have a global space-time of extreme Reissner-Nordstr\" om black holes.

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arXiv1995

BPS Saturated Dyonic Black Holes of $N=8$ Supergravity Vacua

We summarize the results for four-dimensional Bogomol'nyi-Prasad- Sommerfield (BPS) saturated dyonic black hole solutions arising in the Kaluza-Klein sector and the three-form field sector of the eleven-dimensional supergravity on a seven-torus. These black hole solutions break $3\over 4$ of $N=8$ supersymmetry, fill out the multipletes of $U$-duality group, and the two classes of solutions are related to each other by a discrete symmetry transformation in $E_7$. Using the field redefinitions of the corresponding effective actions, we present these solutions in terms of fields describing classes of dyonic black holes carrying charges of $U(1)$ gauge fields in Neveu-Schwarz-Neveu-Schwarz and/or Ramond-Ramond sector(s) of the type-IIA superstring on a six-torus. We also summarize the dependence of their ADM masses on the asymptotic values of scalar fields, parameterizing the toroidal moduli space and the string coupling constant.

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arXiv1995

STATIC FOUR-DIMENSIONAL ABELIAN BLACK HOLES IN KALUZA-KLEIN THEORY

Static, four-dimensional (4-d) black holes (BH's) in ($4+n$)-d Kaluza-Klein (KK) theory with Abelian isometry and diagonal internal metric have at most one electric ($Q$) and one magnetic ($P$) charges, which can either come from the same $U(1)$-gauge field (corresponding to BH's in effective 5-d KK theory) or from different ones (corresponding to BH's with $U(1)_M\times U(1)_E$ isometry of an effective 6-d KK theory). In the latter case, explicit non-extreme solutions have the global space-time of Schwarzschild BH's, finite temperature, and non-zero entropy. In the extreme (supersymmetric) limit the singularity becomes null, the temperature saturates the upper bound $T_H=1/4π\sqrt{|QP|}$, and entropy is zero. A class of KK BH's with constrained charge configurations, exhibiting a continuous electric-magnetic duality, are generated by global $SO(n)$ transformations on the above classes of the solutions.

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arXiv1994

Naked singularities in dilatonic domain wall space-times

We investigate gravitational effects of extreme, non-extreme and ultra- extreme domain walls in the presence of a dilaton field. The dilaton is a scalar field without self-interaction that couples to the matter po- tential that is responsible for the formation of the wall. Motivated by superstring and supergravity theories, we consider both an exponential dilaton coupling (parametrized with the coupling constant alpha and the case where the coupling is self-dual, i.e. it has an extremum for a fi- nite value of the dilaton. For an exponential dilaton coupling, extreme walls (which are static planar configurations with surface energy density sigma_ext saturating the corresponding Bogomol'nyi bound) have a naked (planar) singularity outside the wall for alpha>1, while for alpha smaller or equal to 1 the singularity is null. On the other hand, non-extreme walls (bubbles with two insides and sigma_non > sigma_ext and ultra-extreme walls bubbles of false vacuum decay with sigma_ultra < sigma_ext always have naked singularities. There are solutions with self-dual couplings, which reduce to singularity-free vacuum domain wall space--times. However, only non- and ultra-extreme walls of such a type are dynamically stable.

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arXiv1994

Extreme Domain Wall--Black Hole Complementarity in N=1SUPERGRAVITY with a General Dilaton Coupling

We study supersymmetric (extreme) domain walls in four-dimensional (4d) N=1 supergravity theories with a general dilaton coupling $α> 0$. Type I walls, which are static, planar (say, in ($x,y$) plane) configurations, interpolate between Minkowski space-time and a vacuum with a varying dilaton field. We classify their global space-time with respect to the value of the coupling $α$. $N=1$ supergravity with $α=1$, an effective theory from superstrings, provides a dividing line between the theories with $α>1$, where there is a naked (planar) singularity on one side of the wall, and the theories with $α<1$, where the singularity of the of the wall is covered by the horizon. The global space-time (in $(t,z$) direction) of the extreme walls with the coupling $α$ is the same as the global space-time (in ($t,r)$ direction) of the extreme magnetically charged black holes with the coupling $1/α$.

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arXiv1994

Supergravity Walls as Windows into New Types of Vacua

Within four dimensional (4d) N=1 supergravity theories we present extreme dilatonic domain wall solutions with a general overall coupling $α$ in the dilaton K\" ahler potential. We concentrate on extreme Type I walls, which are static, planar configurations, interpolating between Minkowski space-time and a new type of space-time with a varying dilaton field. $α=0$ case yields extreme ``ordinary'' supergravity walls between Minkowski and anti-de Sitter space-times. For $α=1$ the walls are extreme ``stringy dilatonic'' walls of the three level superstring vacua interpolating between the constant and linear dilaton vacuum. Extreme stringy dilatonic walls ($α=1$) serve as a dividing line between the walls ($0<α<1$) with the (planar) singularity covered by the horizon and those ($α>1$) with the naked singularity. Striking similarities between the global space-time structure of such domain walls and and the one of the corresponding extreme charged black holes with a general dilaton coupling are pointed out.

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arXiv1993

Cosmic Censorship Violation for a Class of Supersymmetric Solitons

We study vacuum domain walls in a class of four-dimensional $N=1$ supergravity theories where along with the matter field, forming the wall, there is more than one ``dilaton'', each respecting $SU(1,1)$ symmetry in their sub-sector. We find {\it supersymmetric} (planar, static) walls, interpolaing between Minkowski vacuum and a new class of supersymmetric vacua which have a naked (planar) singularity. Such walls provide the first example of supersymmetric classical ``solitons'' with naked singularities, and thus violate the (strong) cosmic censorship conjecture within a supersymmetric theory.

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arXiv1993

Ordinary and Dilatonic Domain Walls: Solutions and Induced Space-Times

Recent developments in unifying treatment of domain wall configurations and their global space-time structure is presented. Domain walls between vacua of non-equal cosmological constant fall in three classes depending on the value of their energy density $σ$: (i) extreme walls with $σ=σ_{ext}$ are planar, static walls corresponding to the supersymmetric configurations, (ii) non-extreme walls with $σ>σ_{ext}$ are expanding bubbles with two insides, (iii) ultra-extreme walls with $σ<σ_{ext}$ are bubbles of false vacuum decay. As a prototype exhibiting all three types of configurations vacuum walls between Minkowski and anti-deSitter vacua are discussed. Space-times associated with these walls exhibit non-trivial causal structure closely related to the one of the corresponding extreme and non-extreme charged black holes, however, without singularities. Recently discovered extreme dilatonic walls, pertinent to string theory, are also addressed. They are static, planar domain walls with metric in the string frame being {\it flat} everywhere. Intriguing similarities between the global space-time of dilatonic walls and that of charged dilatonic black holes are pointed out.

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arXiv1993

Flat World of Dilatonic Domain Walls

We study dilatonic domain walls specific to superstring theory. Along with the matter fields and metric the dilaton also changes its value in the wall background. We found supersymmetric (extreme) solutions which in general interpolate between isolated superstring vacua with non-equal value of the matter potential; they correspond to the static, planar domain walls with {\it flat} metric in the string (sigma model) frame. We point out similarities between the space-time of dilatonic walls and that of charged dilatonic black holes. We also comment on non-extreme solutions corresponding to expanding bubbles.

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