arXiv subjects

Mirjam Cvetic

Publications and source records attributed to Mirjam Cvetic.

At least 73 records · Page 4Linked to original sources

arXiv2005

Supersymmetric Kerr--anti-deSitter solutions

We prove the existence of one quarter supersymmetric type IIB configurations that arise as non-trivial scaling solutions of the standard five dimensional Kerr-AdS black holes by the explicit construction of its Killing spinors. This neutral, spinning solution is asymptotic to the static anti-deSitter space-time with cosmological constant $-\textstyle{\frac{1}{\ell^2}}$, it has two finite equal angular momenta $J_1=\pm J_2$, mass $M=\textstyle{\frac{1}{\ell}} (|J_1|+|J_2|)$ and a naked singularity.We also address the scaling limit associated with one half supersymmetric solution with only one angular momentum.

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arXiv2005

Chiral D-brane Models with Frozen Open String Moduli

Most intersecting D-brane vacua in the literature contain additional massless adjoint fields in their low energy spectrum. The existence of these additional fields make it difficult to obtain negative beta functions and, eventually, asymptotic freedom. We address this important issue for N=1 intersecting D-brane models, rephrasing the problems in terms of (open string) moduli stabilization. In particular, we consider a Z2 x Z2 orientifold construction where D6-branes wrap rigid 3-cycles and such extra adjoint fields do not arise. We derive the model building rules and consistency conditions for intersecting branes in this background, and provide N=1 chiral vacua free of adjoint fields. More precisely, we construct a Pati-Salam-like model whose SU(4) gauge group is asymptotically free. We also comment on the application of these results for obtaining gaugino condensation in chiral D-brane models. Finally, we embed our constructions in the framework of flux compactification, and construct new classes of N=1 and N=0 chiral flux vacua.

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arXiv2005

Toward Realistic Intersecting D-Brane Models

We provide a pedagogical introduction to a recently studied class of phenomenologically interesting string models, known as Intersecting D-Brane Models. The gauge fields of the Standard-Model are localized on D-branes wrapping certain compact cycles on an underlying geometry, whose intersections can give rise to chiral fermions. We address the basic issues and also provide an overview of the recent activity in this field. This article is intended to serve non-experts with explanations of the fundamental aspects, and also to provide some orientation for both experts and non-experts in this active field of string phenomenology.

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arXiv2005

Supersymmetric Standard Models, Flux Compactification and Moduli Stabilization

Based on the T-dual constructions of supersymmetric intersecting D6-models on Z_2 x Z_2 orientifolds, whose electroweak sector is parallel with the orientifold planes with Sp(2f)_L x Sp(2f)_R gauge symmetry (hep-th/0407178), we derive and classify Standard Model-like vacua with RR and NSNS fluxes, which stabilize toroidal complex structure moduli and the dilaton. We find consistent four-family (f=4) and two-family (f=2) models with one- and two-units of the quantized flux, respectively. Such models typically possess additional gauge group factors with negative beta functions and may lead, via gaugino condensation, to stabilization of toroidal Kahler moduli. These models have chiral exotics.

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arXiv2005

Standard-like Models as Type IIB Flux Vacua

We construct new semi-realistic Type IIB flux vacua on $Z_2\times Z_2$ orientifolds with three- and four- Standard Model (SM) families and up to three units of quantized flux. The open-string sector is comprised of magnetized D-branes and is T-dual to supersymmetric intersecting D6-brane constructions. The SM sector contains magnetized D9-branes with negative D3-brane charge contribution. There are large classes of such models and we present explicit constructions for representative ones. In addition to models with one and two units of quantized flux, we also construct the first three- and four-family Standard-like models with supersymmetric fluxes, i.e. comprising three units of quantized flux. Supergravity fluxes are due to the self-dual NS-NS and R-R three-form field strength and they fix the toroidal complex structure moduli and the dilaton. The supersymmetry conditions for the D-brane sector fix in some models all three toroidal Kähler moduli. We also provide examples where toroidal K\" ahler moduli are fixed by strong gauge dynamics on the ``hidden sector'' D7-brane. Most of the models possess Higgs doublet pairs with Yukawa couplings that can generate masses for quarks and leptons. The models have (mainly right-) chiral exotics.

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arXiv2004

Supersymmetric Pati-Salam Models from Intersecting D6-branes: A Road to the Standard Model

We provide a systematic construction of three-family N=1 supersymmetric Pati-Salam models from Type IIA orientifolds on $\IT^6/(\IZ_2\times \IZ_2)$ with intersecting D6-branes. All the gauge symmetry factors $SU(4)_C\times SU(2)_L \times SU(2)_R$ arise from the stacks of D6-branes with U(n) gauge symmetries, while the ``hidden sector'' is specified by $USp(n)$ branes, parallel with the orientifold planes or their ${\bf Z_2}$ images. The Pati-Salam gauge symmetry can be broken down to the $SU(3)_C\times SU(2)_L\times U(1)_{B-L} \times U(1)_{I_{3R}}$ via D6-brane splittings, and further down to the Standard Model via D- and F-flatness preserving Higgs mechanism from massless open string states in a N=2 subsector. The models also possess at least two confining hidden gauge sectors, where gaugino condensation can in turn trigger supersymmetry breaking and (some) moduli stabilization. The systematic search yields 11 inequivalent models: 8 models with less than 9 Standard model Higgs doublet-pairs and 1 model with only 2 Standard Model Higgs doublet-pairs, 2 models possess at the string scale the gauge coupling unification of $SU(2)_L$ and $SU(2)_R$, and all the models possess additional exotic matters. We also make preliminary comments on phenomenological implications of these models.

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arXiv2004

D6-brane Splitting on Type IIA Orientifolds

We study the open-string moduli of supersymmetric D6-branes, addressing both the string and field theory aspects of D6-brane splitting on Type IIA orientifolds induced by open-string moduli Higgsing (i.e., their obtaining VEVs). Specifically, we focus on the Z_2 x Z_2 orientifolds and address the symmetry breaking pattern for D6-branes parallel with the orientifold 6-planes as well as those positioned at angles. We demonstrate that the string theory results, i.e., D6-brane splitting and relocating in internal space, are in one to one correspondence with the field theory results associated with the Higgsing of moduli in the antisymmetric representation of Sp(2N) gauge symmetry (for branes parallel with orientifold planes) or adjoint representation of U(N) (for branes at general angles). In particular, the moduli Higgsing in the open-string sector results in the change of the gauge structure of D6-branes and thus changes the chiral spectrum and family number as well. As a by-product, we provide the new examples of the supersymmetric Standard-like models with the electroweak sector arising from Sp(2N)_L x Sp(2N)_R gauge symmetry; and one four-family example is free of chiral Standard Model exotics.

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arXiv2004

General N = 1 Supersymmetric Fluxes in Massive Type IIA String Theory

We study conditions on general fluxes of massive Type IIA supergravity that lead to four-dimensional backgrounds with N = 1 supersymmetry. We derive these conditions in the case of SU(3)- as well as SU(2)-structures. SU(3)-structures imply that the internal space is constrained to be a nearly Kähler manifold with all the turned on fluxes, and the negative cosmological constant proportional to the mass parameter, and the dilaton fixed by the quantized ratio of the three-form and four-form fluxes. We further discuss the implications of such flux vacua with added intersecting D6-branes, leading to the chiral non-Abelian gauge sectors (without orientifold projections). Examples that break SU(3)-structures to SU(2)-ones allow for the internal space conformally flat (up to orbifold and orientifold projections), for which we give an explicit example. These results provide a starting point for further study of the four-dimensional (chiral) N = 1 supersymmetric solutions of massive Type IIA supergravity with D-branes and fluxes, compactified on orientifolds.

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arXiv2004

Supersymmetric Three Family SU(5) Grand Unified Models from Type IIA Orientifolds with Intersecting D6-Branes

We construct some N=1 supersymmetric three-family SU(5) Grand Unified Models from type IIA orientifolds on $\IT^6/(\IZ_2\times \IZ_2)$ with D6-branes intersecting at general angles. These constructions are supersymmetric only for special choices of untwisted moduli. We show that within the above class of constructions there are no supersymmetric three-family models with 3 copies of {\bf 10}-plets unless there are simultaneously some {\bf 15}-plets. We systematically analyze the construction of such models and their spectra. The M-theory lifts of these brane constructions become purely geometrical backgrounds: they are singular $G_2$ manifolds where the Grand Unified gauge symmetries and three families of chiral fermions are localized at codimension 4 and codimension 7 singularities respectively. We also study somepreliminary phenomenological features of the models.

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arXiv2004

Conformal Field Theory Couplings for Intersecting D-branes on Orientifolds

We present a conformal field theory calculation of four-point and three-point correlation functions for the bosonic twist fields arising at the intersections of D-branes wrapping (supersymmetric) homology cycles of Type II orientifold compactifications. Both the quantum contribution from local excitations at the intersections and the world-sheet disk instanton corrections are computed. As a consequence we obtain the complete expression for the Yukawa couplings of chiral fermions with the Higgs fields. The four-point correlation functions in turn lead to the determination of the four-point couplings in the effective theory, and may be of phenomenological interest.

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arXiv2004

General N = 1 Supersymmetric Flux Vacua of (Massive) Type IIA String Theory

We derive conditions for the existence of four-dimensional \N=1 supersymmetric flux vacua of massive type IIA string theory with general supergravity fluxes turned on. For an SU(3) singlet Killing spinor, we show that such flux vacua exist only when the internal geometry is nearly-Kähler. The geometry is not warped, all the allowed fluxes are proportional to the mass parameter and the dilaton is fixed by a ratio of (quantized) fluxes. The four-dimensional cosmological constant, while negative, becomes small in the vacuum with the weak string coupling.

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arXiv2003

Supersymmetric Intersecting D6-branes and Fluxes in Massive Type IIA String Theory

We study N=1 supersymmetric four-dimensional solutions of massive Type IIA supergravity with intersecting D6-branes in the presence NS-NS three-form fluxes. We derive N=1 supersymmetry conditions for the D6-brane and flux configurations in an internal manifold $X_6$ and derive the intrinsic torsion (or SU(3)-structure) related to the fluxes. In the absence of fluxes, N=1 supersymmetry implies that D6-branes wrap supersymmetric three-cycles of $X_6$ that intersect at angles of SU(3) rotations and the geometry is deformed by SU(3)-structures. The presence of fluxes breaks the SU(3) structures to SU(2) and the D6-branes intersect at angles of SU(2) rotations; non-zero mass parameter corresponds to D8-branes which are orthogonal to the common cycle of all D6-branes. The anomaly inflow indicates that the gauge theory on intersecting (massive) D6-branes is not chiral.

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arXiv2003

Cosmological anti-deSitter space-times and time-dependent AdS/CFT correspondence

We study classes of five-dimensional cosmological solutions with negative curvature, which are obtained from static solutions by an exchange of a spatial and temporal coordinate, and in some cases by an analytic continuation. Such solutions provide a suitable laboratory to address the time-dependent AdS/CFT correspondence. For a specific example we address in detail the calculation of the boundary stress-energy and the Wilson line and find disagreement with the standard AdS/CFT correspondence. We trace these discrepancies to the time-dependent effects, such as particle creation, which we further study for specific backgrounds. We also identify specific time-dependent backgrounds that reproduce the correct conformal anomaly. For such backgrounds the calculation of the Wilson line in the adiabatic approximation indicates only a Coulomb repulsion.

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arXiv2003

Time-dependent backgrounds from supergravity with gauged non-compact R-symmetry

We obtain a general class of time-dependent, asymptotically de Sitter backgrounds which solve the first order bosonic equations that extremize the action for supergravity with gauged non-compact $R$-symmetry. These backgrounds correspond only to neutral fields with the correct sign of kinetic energy. Within N=2 five-dimensional supergravity with vector-superfields we provide examples of multi-centered charged black holes in asymptotic de Sitter space, whose spatial part is given by a time-dependent hyper-Kähler space. Reducing these backgrounds to four dimensions yields asymptotically de Sitter multi-centered charged black hole backgrounds and we show that they are related to an instanton configuration by a massive T-duality over time. Within N=2 gauged supergravity in four (and five)-dimensions with hyper-multiplets there could also be neutral cosmological backgrounds that are regular and correspond to the different de Sitter spaces at early and late times.

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arXiv2003

Brane Resolution and Gravitational Chern-Simons terms

We show that gravitational Chern-Simons corrections, associated with the sigma-model anomaly on the M5-brane world-volume, can resolve the singularity of the M2-brane solution with Ricci-flat, special holonomy transverse space. We explicitly find smooth solutions in the cases when the transverse space is a manifold of Spin(7) holonomy and SU(4) holonomy. We comment on the consequences of these results for the holographically related three-dimensional theories living on the world volume of a stack of such resolved M2-branes.

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arXiv2003

More Supersymmetric Standard-like Models from Intersecting D6-branes on Type IIA Orientifolds

We present new classes of supersymmetric Standard-like models from type IIA $\IT^6/(\IZ_2\times \IZ_2)$ orientifold with intersecting D6-branes. D6-branes can wrap general supersymmetric three-cycles of $\IT^6=\IT^2\times \IT^2\times \IT^2$, and any $\IT^2$ is allowed to be tilted. The models still suffer from additional exotics, however we obtained solutions with fewer Higgs doublets, as well as models with all three families of left-handed quarks and leptons arising from the same intersecting sector, and examples of a genuine left-right symmetric model with three copies of left-handed and right-handed families of quarks and leptons.

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arXiv2003

Dynamical Supersymmetry Breaking in Standard-like Models with Intersecting D6-branes

We address dynamical supersymmetry breaking within a N=1 supersymmetric Standard-like Model based on a Z_2 x Z_2 Type IIA orientifold with intersecting D6-branes. The model possesses an additional, confining gauge sector with the USp(2)_A x USp(2)_B x USp(4) gauge group, where the gaugino condensation mechanism allows for the breaking of supersymmetry and stabilizes moduli. We derive the leading contribution to the non-perturbative effective superpotential and determine numerically the minima of the supergravity potential. These minima break supersymmetry and fix two undetermined moduli, which in turn completely specify the gauge couplings at the string scale. For this specific construction the minima have a negative cosmological constant. We expect that for other supersymmetric Standard-like models with intersecting D6-branes, which also possess confining gauge sectors, the supersymmetry breaking mechanism would have qualitatively similar features.

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arXiv2002

A Three-Family Standard-like Orientifold Model: Yukawa Couplings and Hierarchy

We discuss the hierarchy of Yukawa couplings in a supersymmetric three family Standard-like string Model. The model is constructed by compactifying Type IIA string theory on a Z_2 x Z_2 orientifold in which the Standard Model matter fields arise from intersecting D6-branes. When lifted to M theory, the model amounts to compactification of M-theory on a G_2 manifold. While the actual fermion masses depend on the vacuum expectation values of the multiple Higgs fields in the model, we calculate the leading worldsheet instanton contributions to the Yukawa couplings and examine the implications of the Yukawa hierarchy.

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