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J. Sonnenschein

Publications and source records attributed to J. Sonnenschein.

At least 37 records · Page 2Linked to original sources
arXiv1998

Baryons from Supergravity

We study the construction of baryons via supergravity along the line suggested recently by Witten and by Gross and Ooguri. We calculate the energy of the baryon as a function of its size. As expected the energy is linear with N. For the non-supersymmetric theories (in three and four dimensions) we find a linear relation which is an indication of confinement. For the {\cal N} = 4 theory we obtain the result (E L= - {const.}) which is compatible with conformal invariance. Surprisingly, our calculation suggests that there is a bound state of k quarks if N\geq k\geq 5N/8. We study the {\cal N} = 4 theory also at finite temperature and find the zero temperature behavior for small size of the baryon, and screening behaviour for baryon, whose size is large compared to the thermal wavelength.

hep-th↗
arXiv1998

The spectrum of multi-flavor QCD_2 and the non-Abelian Schwinger equation

Massless $QCD_2$ is dominated by classical configurations in the large $N_f$ limit. We use this observation to study the theory by finding solutions to equations of motion, which are the non-Abelian generalization of the Schwinger equation. We find that the spectrum consists of massive mesons with $M^2={e^2 N_f\over 2π}$ which correspond to Abelian solutions. We generalize previously discovered non-Abelian solutions and discuss their interpretation. We prove a no-go theorem ruling out the existence of soliton solutions. Thus the semi-classical approximation shows no baryons in the case of massless quarks, a result derived before in the strong-coupling limit only.

hep-th↗
arXiv1998

Wilson Loops in the Large N Limit at Finite Temperature

Using a proposal of Maldacena we compute in the framework of the supergravity description of N coincident D3 branes the energy of a quark anti-quark pair in the large N limit of U(N) N=4 SYM in four dimensions at finite temperature.

hep-th↗
arXiv1998

More on Probing Branes with Branes

We generalize the Gibbons-Wiltshire solution of four dimensional Kaluza-Klein black holes in order to describe Type IIA solutions of bound states of D6 and D0-branes. We probe the solutions with a D6-brane and a D0-brane. We also probe a system of D2+D0-branes and of a D2-brane bound to a F1-string with a D2-brane. A precise agreement between the SYM and the SUGRA calculations is found for the static force as well as for the $v^2$ force in all cases.

hep-th↗
arXiv1997

On the M-Theory Approach to (Compactified) 5D Field Theories

We construct M-theory curves associated with brane configurations of SU(N), SO(N) and $Sp(2N)$ 5d supersymmetric gauge theories compactified on a circle. From the curves we can account for all the existing different SU(N) field theories with $N_f \leq 2 N$. This is the correct bound for $N \geq 3$. We remark on the exceptional case SU(2). The bounds obtained for SO(N) and $Sp(2N)$ are $N_f\leq N-4$ and $N_f\leq 2N+4$, respectively.

hep-th↗
arXiv1997

The string tension in massive $QCD_2$

We compute the string tension in massive $QCD_2$. It is shown that the string tension vanishes when the mass of the dynamical quark is zero, with no dependence on the representations of the dynamical or of the external charges. When a small mass ($m\ll e$) is added, a tension appears and we calculate its value as a function of the representations.

hep-th↗
arXiv1997

More on Screening and Confinement in 2D QCD

We provide further evidence for the screening behavior of massless SU(N_c) bosonized QCD by (i) computing the potential between external quarks, (ii) bosonizing also the external sources and analyzing the states of the combined system and (iii) using an expansion in N_f- the number of flavors. We write down novel "non-abelian Schwinger like" solutions of the equations of motion, compute their masses and argue that an exchange of massive modes of this type is associated with the screening mechanism. Confinement for massive dynamical fermions is shown using (ii) and (iii). We show the screening behavior of the N=1 super Yang Mills theory, by applying a point splitting method to the scalar current.

hep-th↗
arXiv1997

Comments on the M Theory Approach to N=1 SQCD and Brane Dynamics

We use the M theory approach of Witten to investigate N=1 SU($N_c$) SQCD with $N_f$ flavors. We reproduce the field theoretical results and identify in M theory the gluino condensate and the eigenvalues of the meson matrix. This approach allows us to identify the constant piece of the effective field theory coupling from which the coefficient of the one-loop $β$-function can be identified. By studying the area of the M-theory five-brane we investigate the stability of type IIA brane configurations. We prove that in a supersymmetric setup there is no force between static D4-branes that end on NS five-branes. The force in the case that there is a relative velocity between the branes is computed. We show that at the regions of intersecting IIA branes the curvature of the M theory five-brane is singular in the type IIA limit.

hep-th↗
arXiv1997

Novel field theory phenomena from F theory and D-branes

Talk presented in the 97 Karpatcz winter school. We describe Sen's work on F theory on K3 and its reflection on the world-volume field theory on a D3-brane probe. Field theories on a multiple of probes are analyzed. We construct a 4d N=1 superconformal probe theory which is invariant under electric-magnetic duality via a compactification to six dimensions on T^6/Z_2 x Z_2.

hep-th↗
arXiv1997

Brane Configurations and 4D Field Theory Dualities

We study brane configurations which correspond to field theories in four dimension with N=2 and N=1 supersymmetry. In particular we discuss brane motions that translate to Seiberg's duality in N=1 models recently studied by Elitzur, Giveon and Kutasov. We investigate, using the brane picture, the moduli spaces of the dual theories. Deformations of these models like mass terms and vacuum expectation values of scalar fields can be identified with positions of branes. The map of these deformations between the electric and dual magnetic theories is clarified. The models we study reproduce known field theory results and we provide an example of new dual pairs with N=1 supersymmetry. Possible relations between brane configurations and non-supersymmetric field theories are discussed.

hep-th↗
arXiv1997

Screening and confinement in large N_f QCD_2 and in N=1 SYM_2

The screening nature of the potential between external quarks in massless $SU(N_c)$ $QCD_2$ is derived using an expansion in $N_f$- the number of flavors. Applying the same method to the massive model, we find a confining potential. We consider the N=1 super Yang Mills theory, reveal certain problematic aspects of its bosonized version and show the associated screening behavior by applying a point splitting method to the scalar current.

hep-th↗
arXiv1996

Non-Perturbative Properties of Heterotic String Vacua Compactified on ${K3\times T^2}$

Using the heterotic--type II duality of $N=2$ string vacua in four space-time dimensions we study non-perturbative couplings of toroidally compactified six-dimensional heterotic vacua. In particular, the heterotic--heterotic $S$-duality and the Coulomb branch of tensor multiplets observed in six dimensions are studied from a four-dimensional point of view. We explicitly compute the couplings of the vector multiplets of several type II vacua and investigate the implications for their heterotic duals.

hep-th↗
arXiv1995

On the Relation Between the Holomorphic Prepotential and the Quantum Moduli in SUSY Gauge Theories

We give a simple proof of the relation $Λ\p_artialΛ\F= {i\over2π}b_1\langle\Trϕ^2\rangle$, which is valid for $N=2$ supersymmetric QCD with massless quarks. We consider $SU(N_c)$ gauge theories as well as $SO(N_c)$ and $SP(N_c)$. Aa analogous relation which corresponds to massive hypermultiplets is written down. We also discuss the generalizations to $N=1$ models in the Coulomb phase.

hep-th↗
arXiv1995

The "Dual" Variables Of Yang-Mills Theory And Local Gauge Invariant Variables

After adding auxiliary fields and integrating out the original variables, the Yang-Mills action can be expressed in terms of local gauge invariant variables. This method reproduces the known solution of the two dimensional $SU(N)$ theory. In more than two dimensions the action splits into a topological part and a part proportional to $α_s$. We demonstrate the procedure for $SU(2)$ in three dimensions where we reproduce a gravity-like theory. We discuss the four dimensional case as well. We use a cubic expression in the fields as a space-time metric to obtain a covariant Lagrangian. We also show how the four-dimensional $SU(2)$ theory can be expressed in terms of a local action with six degrees of freedom only.

hep-th↗
arXiv1995

Mesonic Spectra of Bosonized QCD_2 Models

We discuss bosonized two-dimensional QCD with massless fermions in the adjoint and multi-flavor fundamental representations. We evaluate the massive mesonic spectra of several models by using the light-front quantization and diagonalizing the mass operator $M^2=2P^+P^- $. We recover previous results in the case of one flavor adjoint fermions and we find the exact massive spectrum of multi flavor QCD in the limit of large number of flavors.

hep-th↗
arXiv1995

Flows and Duality Symmetries in N=1 Supersymmetric Gauge Theories

We present more examples of dual N=1 SUSY gauge theories. This set of theories is connected by flows to both Seiberg's and Kutasov's dual theories. This provides a unifying picture of the various dual theories. We investigate the dual theories, their flat directions and mass perturbations.

hep-th↗
arXiv1994

The String Theory Approach to Generalized 2D Yang-Mills Theory

We calculate the partition function of the $SU(N)$ ( and $U(N)$) generalized $YM_2$ theory defined on an arbitrary Riemann surface. The result which is expressed as a sum over irreducible representations generalizes the Rusakov formula for ordinary YM_2 theory. A diagrammatic expansion of the formula enables us to derive a Gross-Taylor like stringy description of the model. A sum of 2D string maps is shown to reproduce the gauge theory results. Maps with branch points of degree higher than one, as well as ``microscopic surfaces'' play an important role in the sum. We discuss the underlying string theory.

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