arXiv subjects

Radu Tatar

Publications and source records attributed to Radu Tatar.

At least 73 records · Page 4Linked to original sources

arXiv2002

Open/Closed String Dualities and Seiberg Duality from Geometric Transitions in M-theory

We propose a general method to study open/closed string dualities from transitions in M theory which is valid for a large class of geometrical configurations. By T-duality we can transform geometrically engineered configurations into N = 1 brane configurations and study the transitions of the corresponding branes by lifting the configurations to M-theory. We describe the transformed degenerated M5 branes and extract the field theory information on gluino condensation by factorization of the Seiberg-Witten curve. We also include massive flavors and orientifolds and discuss Seiberg duality which appears in this case as a birational flop. After the transition, the Seiberg duality becomes an abelian electric-magnetic duality.

hep-th↗

arXiv2002

Orbifolds, Penrose Limits and Supersymmetry Enhancement

We consider supersymmetric PP-wave limits for different N=1 orbifold geometries of the five sphere S^5 and the five dimensional Einstein manifold T^{1,1}. As there are several interesting ways to take the Penrose limits, the PP-wave geometry can be either maximal supersymmetric N=4 or half-maximal supersymmetric N=2. We discuss in detail the cases AdS_5 x S^5/Z_3, AdS_5 x S^5/(Z_m x Z_n) and AdS_5 x T^{1,1}/(\Z_m \times \Z_n) and we identify the gauge invariant operators which correspond to stringy excitations for the different limits.

hep-th↗

arXiv2002

Geometric Transition versus Cascading Solution

We study Vafa's geometric transition and Klebanov - Strassler solution from various points of view in M-theory. In terms of brane configurations, we show the detailed equivalences between the two models. In some limits, both models have an alternative realization as fourfolds in M-theory with appropriate G-fluxes turned on. We discuss some aspects of the fourfolds including how to see the transition and a possible extension to the non-supersymmetric case.

hep-th↗

arXiv2001

Geometric Transition, Large N Dualities and MQCD Dynamics

We study Vafa's geometric transition from a brane setup in M-theory. In this transition D5 branes wrapped on P^1 cycles of a resolved conifold disappear and are replaced by fluxes on a deformed conifold. In the limit of small sized P^1, we describe this mechanism as a transition from curved M5 branes to plane M5 branes which replaces SU(N) MQCD by U(1) theories on the bulk. This agrees with the results expected from the geometric transition. We also discuss the reduction to ten dimensions and a brane creation mechanism in the presence of fluxes.

hep-th↗

arXiv2001

Orientifold, Geometric Transition and Large N Duality for SO/Sp Gauge Theories

We extend the large N duality of four dimensional N=1 supersymmetric Yang-Mills theory with additional chiral fields and arbitrary superpotential recently proposed by Cachazo, Intriligator and Vafa to the case of SO/Sp gauge groups. By orientifolding the geometric transition, we investigate a large N duality between N=1, SO/Sp supersymmetric theories with arbitrary superpotential and an Abelian N=2 theory with supersymmetry broken to N=1 by electric and magnetic Fayet-Iliopoulos terms.

hep-th↗

arXiv2000

T-duality and Actions for Non-Commutative D-Branes

We show how the T-duality is realized for D-branes with noncommutative world-volume coordinates. We discuss D-branes wrapped on tori and the result is that the recently found noncommutative actions form a consistent collection due to the T-duality mapping between noncommutative D-branes and rotated commutative D-branes on deformed tori.

hep-th↗

arXiv2000

A Note on Non-Commutative Field Theory and Stability of Brane-Antibrane Systems

It has been conjectured that a pair of D5 - anti D5 branes wrapped on some non-trivial two cycle of a Calabi-Yau manifold becomes a stable BPS D3 brane in the presence of a very large B field and magnetic fluxes on their worldvolumes. We discuss this by considering the non-commutative field theory on the worldvolume of the pair of branes whose field multiplication is made with respect to two different * products due to the presence of different F fields on the two branes. The tachyonic field becomes massless for a specific choice of the magnetic fluxes and it allows a trivial solution. Our discussion generalizes recent results concerning stability of brane-antibrane systems on Calabi-Yau spaces to the case of non-commutative branes.

hep-th↗

arXiv2000

Conifolds with Discrete Torsion and Noncommutativity

We study D3 branes at orbifolded conifold singularities in the presence of discrete torsion. The vacuum moduli space of open strings becomes non-commutative due to a deformation of the superpotential and is studied via the representation theory of the moduli algebra. It is also shown that the center of the moduli algebra correctly describes the underlying orbifolded conifolds. The field theory can be obtained by a marginal deformation of the ${\cal N} = 1$ gauge theory on D3 branes at conifold singularity, the global symmetry being broken from $SU(2) \times SU(2)$ to $U(1) \times U(1)$. By using the AdS/CFT correspondence we argue that the marginal deformation is related to massless KK modes of NSNS and RR two form reduced on the compact space $T^{1,1}$. We build a $T^2$ fibration of $T^{1,1}$ and show that a D3 brane in the bulk correspond to a D5 brane on the $T^2$ fibre. We also discuss the possible brane construction of the system.

hep-th↗

arXiv2000

Renormalization Group Flows on D3 branes at an Orbifolded Conifold

We consider D3-branes at an orbifolded conifold whose horizon ${X_5}$ resolves into a smooth Einstein manifold which joins several copies of ${\bf T}^{1,1}$. We describe in details the resolution of the singular horizon ${X_5}$ and describe different types of two-cycles appearing in the resolution. For a large number of D3 branes, the AdS/CFT conjecture becomes a duality between type IIB string theory on $AdS_5 \times {X_5} $ and the ${\cal N} = 1$ field theory living on the D3 branes. We study the fractional branes as small perturbations of the string background and we reproduce the logarithmic flow of field theory couplings by studying fluxes of NS-NS and R-R two forms through different 2-cycles of the resolved horizon.

hep-th↗

arXiv1999

Non-BPS Branes on a Calabi-Yau Threefold and Bose-Fermi Degeneracy

We consider the spectrum of open strings for non-BPS D-brane configuration in type II string theory on a Calabi-Yau threefold. In general, there is no degeneracy between bosonic and fermionic states. However we find special values for the moduli space of Calabi-Yau threefolds there are non-BPS brane configurations which have an exact degeneracy between bosonic and fermionic states. For these values there is no force between pairs of non-BPS D-branes. This gives rise to a possibility of building diverse non-supersymmetric gauge field theories on the brane world-volume. We use the approach recently elaborated by Gaberdiel and Sen.

hep-th↗

arXiv1999

Quantum Spacetimes and Finite N Effects in 4D Super Yang-Mills Theories

The truncation in the number of single-trace chiral primary operators of $\N=4$ SYM and its conjectured connection with gravity on quantum spacetimes are elaborated. The model of quantum spacetime we use is $AdS^5_q \times S^5_q$ for $q$ a root of unity. The quantum sphere is defined as a homogeneous space with manifest $SU_q(3)$ symmetry, but as anticipated from the field theory correspondence, we show that there is a hidden $SO_q(6)$ symmetry in the constrution. We also study some properties of quantum space quotients as candidate models for the quantum spacetime relevant for some $Z_n$ quiver quotients of the $\N=4$ theory which break SUSY to $\N=2$. We find various qualitative agreements between the proposed models and the properties of the corresponding finite $N$ gauge theories.

hep-th↗

arXiv1999

Moduli Space for Conifolds as Intersection of Orthogonal D6 branes

We show that a system of parallel D3 branes near a conifold singularity can be mapped onto an intersecting configuration of orthogonal branes in type IIA string theory. Using this brane configuration, we analyze the Higgs moduli space of the associated field theory. The dimension of the Higgs moduli space is computed from a geometrical analysis of the conifold singularity. Our results provide evidence for an extended s-rule. In addition, a discrepancy between the prediction of the brane configuration and the result obtained from a geometrical anaysis is noted. This discrepancy is traced back to worldsheet instanton effects.

hep-th↗

arXiv1999

Branes at Orbifolded Conifold Singularities and Supersymmetric Gauge Field Theories

We consider D3 branes at orbifolded conifold singularities which are not quotient singularities. We use toric geometry and gauged linear sigma model to study the moduli space of the gauge theories on the D3 branes. We find that topologically distinct phases are related by a flop transition. It is also shown that an orbifold singularity can occur in some phases if we give expectation values to some of the chiral fields.

hep-th↗

arXiv1999

The Large N Limit of ${\cal N}=1$ Field Theories from F Theory

We study AdS/CFT correspondence in four dimensional N=1 field theories realized on the worldvolume of D3 branes near the intersections between D7 and D7' branes in F theory studied by Aharony et al. We consider the compactification of F theory on elliptically fibered Calabi-Yau threefolds corresponding to two sets of parallel D7 branes sharing six spacetime directions. This can be viewed as orbifolds of six torus T^6 by Z_p x Z_q (p, q=2, 3, 4, 6). We find the large N spectrum of chiral primary operators by exploiting the property of AdS/CFT correspondence. Moreover, we discuss supergravity solutions for D3 branes in D7 and D7' branes background.

hep-th↗

arXiv1999

Comments on Brane Configurations with Semi-infinite D4 Branes

We consider four dimensional supersymmetric gauge field theories from brane configurations with the matter content given by semi-infinite D4 branes ending on both sides of NS branes. In M theory configuration, we discuss the splitting of the M5 brane into infinite cylindrical M5 branes (which decouple) and transversal M5 brane. The splitting condition appears naturally from the consistency of the different projections of the Seiberg-Witten curve.

hep-th↗

arXiv1999

Branes, Orbifolds and the Three Dimensional ${\cal N} = 2$ SCFT in the Large N limit

We study the correspondence between the large $N$ limit of ${\cal N} = 2$ three dimensional superconformal field theories and M theory on orbifolds of $AdS_4 \times {\bf S^7}$. We identify the brane configuration which gives $C^3/Z_3$ as a background for the M theory in terms of a Brane Box Model or a (p, q) web model. By taking the orbifold projection on the known spectrum of Kaluza-Klein harmonics of supergravity, we obtain information about the chiral primary operators at the orbifold singularities.

hep-th↗

arXiv1999

Comments on $SO/Sp$ Gauge Theories from Brane Configurations with an O6 Plane

We use the M theory approach in the presence of an orientifold O6 plane to understand some aspects of the moduli space of vacua for N=1 supersymmetric $SO(N_c)/Sp(N_c)$ gauge theories in four dimensions. By exploiting some general properties of the O6 orientifold, we reproduce some results obtained previously with an orientifold O4 plane when the flavor group arises from the worldvolume dynamics of D6 branes. By using semi-infinite D4 branes instead of D6 branes, we derive the most general form of the rotated curve describing the moduli space of vacua for N=1 supersymmetric gauge theory with massive matter.

hep-th↗

arXiv1998

Higher Derivative Terms from Threebranes in F Theory

The computation of higher derivative corrections to the low energy effective actions of ${\cal N}=2$ gauge theories is considered. In particular, higher derivative corrections are computed for four dimensional ${\cal N}=2$ super Yang-Mills theory with gauge group SU(2) and $N_f=4$ hypermultiplets in the fundamental representation. The four derivative terms computed in an approach which realizes the gauge theory as the world volume theory of three branes in F theory are in agreement with the field theory result.

hep-th↗