arXiv subjects

Mirjam Cvetič

Publications and source records attributed to Mirjam Cvetič.

60 records · Page 4Linked to original sources

arXiv1995

BPS Saturated and Non-Extreme States in Abelian Kaluza-Klein Theory and Effective N=4 Supersymmetric String Vacua

We summarize results for all four-dimensional Bogomol'nyi-Sommerfield-Prasat (BPS) saturated and non-extreme solutions of the ($4+n$)-dimensional Abelian Kaluza-Klein theory. Within effective N=4 supersymmetric string vacua, parameterized in terms of fields of the heterotic string on a six-torus, we then present a class of BPS saturated states and the corresponding non-extreme solutions, specified by $O(6,22,Z)$ and $SL(2,Z)$ orbits of general dyonic charge configurations with zero axion. The BPS saturated states with non-negative $O(6,22,Z)$ norms for electric and magnetic charge vectors, along with the corresponding set of non-extreme solutions, are regular with non-zero masses. BPS saturated states with the negative charge norms are singular, unaccompanied by non-extreme solutions and become massless at particular points of the moduli space. The role that such massless states may play in the enhancement of non-Abelian gauge symmetry as well as local supersymmetry is addressed.

hep-th↗

arXiv1995

Four-dimensional supersymmetric dyonic black holes in eleven-dimensional supergravity

A class of 4-dimensional supersymmetric dyonic black hole solutions that arise in an effective 11-dimensional supergravity compactified on a 7-torus is presented. We give the explicit form of dyonic solutions with diagonal internal metric, associated with the Kaluza-Klein sector as well as the three-form field, and relate them to a class of solutions with a general internal metric by imposing a subset of $SO(7)\subset E_7$ transformations. We also give the field transformations which relate the above configurations to 4-dimensional ground state configurations of Ramond-Ramond and Neveu-Schwarz-Neveu-Schwarz sector of type-IIA strings on a 6-torus.

hep-th↗

arXiv1994

Supersymmetric Dyonic Black Holes in Kaluza-Klein Theory

We study supersymmetric, four-dimensional (4-d), Abelian charged black holes (BH's) arising in (4+n)-d (1 \le n \le 7) Kaluza-Klein (KK) theories. Such solutions, which satisfy supersymmetric Killing spinor equations (formally satisfied for any n) and saturate the corresponding Bogomol'nyi bounds, can be obtained if and only if the isometry group of the internal space is broken down to the U(1)_E \times U(1)_M gauge group; they correspond to dyonic BH's with electric Q and magnetic P charges associated with {\it different} U(1) factors. The internal metric of such configurations is diagonal with (n-2) internal radii constant, while the remaining two radii (associated with the respective electric and magnetic U(1) gauge fields) and the 4-d part of the metric turn out to be independent of n, i.e., solutions are effectively those of supersymmetric 4-d BH's of 6-d KK theory. For Q \ne 0 and P \ne 0, 4-d space-time has a null singularity, finite temperature (T_H \propto 1 / \sqrt{|QP|}) and zero entropy. Special cases with either Q=0 or P=0 correspond to the supersymmetric 4-d BH's of 5-d KK theory, first derived by Gibbons and Perry, which have a naked singularity and infinite temperature.

hep-th↗

arXiv1993

Local and global gravitational aspects of domain wall space-times

Local and global gravitational effects induced by eternal vacuum domain walls are studied. We concentrate on thin walls between non-equal and non-positive cosmological constants on each side of the wall. These vacuum domain walls fall in three classes depending on the value of their energy density $σ$: (1)\ extreme walls with $σ= σ_{\text{ext}}$ are planar, static walls corresponding to supersymmetric configurations, (2)\ non-extreme walls with $σ= σ_{\text{non}} > σ_{\text{ext}}$ correspond to expanding bubbles with observers on either side of the wall being {\em inside\/} the bubble, and (3)\ ultra-extreme walls with $σ= σ_{\text{ultra}} < σ_{\text{ext}}$ represent the bubbles of false vacuum decay. On the sides with less negative cosmological constant, the extreme, non-extreme, and ultra-extreme walls exhibit no, repulsive, and attractive effective ``gravitational forces,'' respectively. These ``gravitational forces'' are global effects not caused by local curvature. Since the non-extreme wall encloses observers on both sides, the supersymmetric system has the lowest gravitational mass accessable to outside observers. It is conjectured that similar positive mass protection occurs in all physical systems and that no finite negative mass object can exist inside the universe. We also discuss the global space-time structure of these singularity free space-times and point out intriguing analogies with the causal structure of black holes.

gr-qc↗

arXiv1993

Non-Extreme and Ultra-Extreme Domain Walls and Their Global Space-Times

Non-extreme walls (bubbles with two insides) and ultra-extreme walls (bubbles of false vacuum decay) are discussed. Their respective energy densities are higher and lower than that of the corresponding extreme (supersymmetric), planar domain wall. These singularity free space-times exhibit non-trivial causal structure analogous to certain non-extreme black holes. We focus on anti-de~Sitter--Minkowski walls and comment on Minkowski--Minkowski walls with trivial extreme limit, as well as walls adjacent to de~Sitter space-times with no extreme limit.

hep-th↗

arXiv1992

$V'Z$ and $V'W$ Production as Tests of Heavy Gauge Boson Couplings at Future Hadron Colliders

We point out that the production cross section of $pp\to V'V$, with $V'=W',Z'$ and $V=W,Z$ is a useful diagnostic of $V'$ gauge couplings at future hadron colliders. For $M_{Z'}\simeq1$ TeV it would allow determination of combinations of $Z'$ gauge couplings to the quarks to around 10 percent. An analysis of the extraction of gauge couplings from the complementary tests: forward-backward asymmetry, rare decays $pp\to V'\to f_1{\bar f_2}V$, and the production cross section $pp\to V'V$ is given in a model-independent framework. Four ratios of charges are needed to characterize a general gauge theory with an additional family-independent $U_1'$ factor. We show that there are four functions of these ratios observable at hadron colliders, but for projected SSC and LHC luminosities only two combinations can be extracted. These yield a significant discrimination between interesting GUT-motivated models. Clean tests of whether a new $W'$ couples to right-handed currents, of the ratio $g_R/g_L$ of gauge couplings, and of the non-abelian vertex in left-right symmetric models are described.

hep-ph↗