1,402 research outputs found
Comments on (Non-)Chiral Gauge Theories and Type IIB Branes
We use type IIB brane configurations which were recently suggested by Hanany
and Zaffaroni to study four dimensional N=1 supersymmetric gauge theories. We
calculate the one loop beta function and realize Seiberg's duality using a
particular configuration. We also comment on the anomaly cancelation condition
in the case of chiral theories and the beta function in the case of chiral and
SO/Sp theories.Comment: 11 pages, Latex. 5 figures. Several changes in text and a reference
was added. Accepted to Phys.Lett.
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
Quantum MHV Diagrams
Over the past two years, the use of on-shell techniques has deepened our
understanding of the S-matrix of gauge theories and led to the calculation of
many new scattering amplitudes. In these notes we review a particular on-shell
method developed recently, the quantum MHV diagrams, and discuss applications
to one-loop amplitudes. Furthermore, we briefly discuss the application of
D-dimensional generalised unitarity to the calculation of scattering amplitudes
in non-supersymmetric Yang-Mills.Comment: 17 pages, 7 figures; based on two talks given at the 7th Workshop On
Continuous Advances In QCD, 11-14 May 2006, Minneapolis, Minnesot
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
Crystal Manyfold Universes in AdS Space
We derive crystal braneworld solutions, comprising of intersecting families
of parallel -branes in a -dimensional space. Each family
consists of alternating positive and negative tension branes. In the simplest
case of exactly orthogonal families, there arise different crystals with
unbroken 4D Poincare invariance on the intersections, where our world can
reside. A crystal can be finite along some direction, either because that
direction is compact, or because it ends on a segment of bulk, or
infinite, where the branes continue forever. If the crystal is interlaced by
connected 3-branes directed both along the intersections and orthogonal to
them, it can be viewed as an example of a Manyfold universe proposed recently
by Arkani-Hamed, Dimopoulos, Dvali and the author. There are new ways for
generating hierarchies, since the bulk volume of the crystal and the lattice
spacing affect the 4D Planck mass. The low energy physics is sensitive to the
boundary conditions in the bulk, and has to satisfy the same constraints
discussed in the Manyfold universe. Phenomenological considerations favor
either finite crystals, or crystals which are infinite but have broken
translational invariance in the bulk. The most distinctive signature of the
bulk structure is that the bulk gravitons are Bloch waves, with a band
spectrum, which we explicitly construct in the case of a 5-dimensional theory.Comment: 16 pages, latex, no figures. v2: comments added and misprints
correcte
Branes at Singularities in Type 0 String Theory
We consider Type 0B D3-branes placed at conical singularities and analyze in
detail the conifold singularity. We study the non supersymmetric gauge theories
on their worldvolume and their conjectured dual gravity descriptions. In the
ultraviolet the solutions exhibit a logarithmic running of the gauge coupling.
In the infrared we find confining solutions and IR fixed points.Comment: 18 pages, uses BibTeX, ssg.bs
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
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