120 research outputs found
Self-Dual Strings and Stability of BPS States in N=2 SU(2) Gauge Theories
We show how BPS states of supersymmetric SU(2) Yang-Mills with matter -both
massless and massive- are described as self-dual strings on a Riemann surface.
This connection enables us to prove the stability and the strong coupling
behaviour of these states. The Riemann surface naturally arises from type-IIB
Calabi-Yau compactifications whose three-branes wrapped around vanishing
two-cycles correspond to one-cycles on this surface.Comment: 27 LaTex with figs., Some changes in W-boson decay discussion, Refs.
adde
Wilson loops from multicentre and rotating branes, mass gaps and phase structure in gauge theories
Within the AdS/CFT correspondence we use multicentre D3-brane metrics to
investigate Wilson loops and compute the associated heavy quark-antiquark
potentials for the strongly coupled SU(N) super-Yang-Mills gauge theory, when
the gauge symmetry is broken by the expectation values of the scalar fields.
For the case of a uniform distribution of D3-branes over a disc, we find that
there exists a maximum separation beyond which there is no force between the
quark and the antiquark, i.e. the screening is complete. We associate this
phenomenon with the possible existence of a mass gap in the strongly coupled
gauge theory. In the finite-temperature case, when the corresponding
supergravity solution is a rotating D3-brane solution, there is a class of
potentials interpolating between a Coulombic and a confining behaviour.
However, above a certain critical value of the mass parameter, the potentials
exhibit a behaviour characteristic of statistical systems undergoing phase
transitions. The physical path preserves the concavity property of the
potential and minimizes the energy. Using the same rotating-brane solutions, we
also compute spatial Wilson loops, associated with the quark-antiquark
potential in models of three-dimensional gauge theories at zero temperature,
with similar results.Comment: 27 pages, latex, 7 figures; v2: no substantial changes, version to
appear in Adv. Theor. Math. Phy
Periods, Coupling Constants and Modular Functions in N=2 SU(2) SYM with Massive Matter
We determine the mass dependence of the coupling constant for N=2 SYM with
N_f=1,2,3 and 4 flavours. All these cases can be unified in one analytic
expression, given by a Schwarzian triangle function. Moreover we work out the
connection to modular functions which enables us to give explicit formulas for
the periods. Using the form of the J-functions we are able to determine in an
elegant way the couplings and monodromies at the superconformal points.Comment: Some changes, final version to appear in IJMPA. 14 LaTex page
PP-waves from rotating and continuously distributed D3-branes
We study families of PP-wave solutions of type-IIB supergravity that have
(light-cone) time dependent metrics and RR five-form fluxes. They arise as
Penrose limits of supergravity solutions that correspond to rotating or
continuous distributions of D3-branes. In general, the solutions preserve
sixteen supersymmetries. On the dual field theory side these backgrounds
describe the BMN limit of N=4 SYM when some scalars in the field theory have
non-vanishing expectation values. We study the perturbative string spectrum and
in several cases we are able to determine it exactly for the bosons as well as
for the fermions. We find that there are special states for particular values
of the light-cone constant P_+.Comment: 23 pages, Latex. v2: a few extra remarks and aesthetic changes,
version to appear in JHE
Domain walls of gauged supergravity, M-branes, and algebraic curves
We provide an algebraic classification of all supersymmetric domain wall
solutions of maximal gauged supergravity in four and seven dimensions, in the
presence of non-trivial scalar fields in the coset SL(8,R)/SO(8) and
SL(5,R)/SO(5) respectively. These solutions satisfy first-order equations,
which can be obtained using the method of Bogomol'nyi. From an
eleven-dimensional point of view they correspond to various continuous
distributions of M2- and M5-branes. The Christoffel-Schwarz transformation and
the uniformization of the associated algebraic curves are used in order to
determine the Schrodinger potential for the scalar and graviton fluctuations on
the corresponding backgrounds. In many cases we explicitly solve the
Schrodinger problem by employing techniques of supersymmetric quantum
mechanics. The analysis is parallel to the construction of domain walls of
five-dimensional gauged supergravity, with scalar fields in the coset
SL(6,R)/SO(6), using algebraic curves or continuous distributions of D3-branes
in ten dimensions. In seven dimensions, in particular, our classification of
domain walls is complete for the full scalar sector of gauged supergravity. We
also discuss some general aspects of D-dimensional gravity coupled to scalar
fields in the coset SL(N,R)/SO(N).Comment: 46 pages, latex. v2: typos corrected and some references added. v3:
minor corrections and improvements, references added, to appear in ATM
Riemann surfaces and Schrodinger potentials of gauged supergravity
Supersymmetric domain-wall solutions of maximal gauged supergravity are
classified in 4, 5 and 7 dimensions in the presence of non-trivial scalar
fields taking values in the coset SL(N, R)/SO(N) for N=8, 6 and 5 respectively.
We use an algebro-geometric method based on the Christoffel-Schwarz
transformation, which allows for the characterization of the solutions in terms
of Riemann surfaces whose genus depends on the isometry group. The
uniformization of the curves can be carried out explicitly for models of low
genus and results into trigonometric and elliptic solutions for the scalar
fields and the conformal factor of the metric. The Schrodinger potentials for
the quantum fluctuations of the graviton and scalar fields are derived on these
backgrounds and enjoy all properties of supersymmetric quantum mechanics.
Special attention is given to a class of elliptic models whose quantum
fluctuations are commonly described by the generalized Lame potential
\mu(\mu+1)P(z) + \nu(\nu+1)P(z+\omega_1)+ \kappa(\kappa+1)P(z+\omega_2) +
\lambda(\lambda+1)P(z+\omega_1 +\omega_2) for the Weierstrass function P(z) of
the underlying Riemann surfaces with periods 2\omega_1 and 2\omega_2, for
different half-integer values of the coupling constants \mu, \nu, \kappa,
\lambda.Comment: 13 pages, latex; contribution to the proceedings of the TMR meeting
"Quantum Aspects of Gauge Theories, Supersymmetry and Unification" held in
Paris in September 199
The three-dimensional BF Model with Cosmological Term in the Axial Gauge
We quantize the three-dimensional -model using axial gauge conditions.
Exploiting the rich symmetry-structure of the model we show that the
Green-functions correspond to tree graphs and can be obtained as the unique
solution of the Ward-Identities. Furthermore, we will show that the theory can
be uniquely determined by symmetry considerations without the need of an action
principle.Comment: one reference added, transmission errors correcte
Integrability and maximally helicity violating diagrams in n=4 supersymmetric yang-mills theory.
We apply maximally helicity violating (MHV) diagrams to the derivation of the one-loop dilatation operator of N=4 supersymmetric Yang-Mills theory in the SO(6) sector. We find that in this approach the calculation reduces to the evaluation of a single MHV diagram in dimensional regularization. This provides the first application of MHV diagrams to an off-shell quantity. We also discuss other applications of the method and future directions
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