353 research outputs found
Gauge Instantons from Open Strings
In this contribution we describe how to obtain instanton effects in four
dimensional gauge theories by computing string scattering amplitudes in
D3/D(-1) brane systems. In particular we show that the disks with mixed
boundary conditions, which are typical of the D3/D(-1) system, are the sources
for the classical instanton solution.Comment: 7 pages, 2 figures, Contribution to the proceedings of the 36th
International Symposium Ahrenshoop, Berlin, Germany, 26-30 August 200
The effective theory of the Calogero- Sutherland model and Luttinger systems.
We construct the effective field theory of the Calogero-Sutherland model in
the thermodynamic limit of large number of particles . It is given by a
\winf conformal field theory (with central charge ) that describes {\it
exactly} the spatial density fluctuations arising from the low-energy
excitations about the Fermi surface. Our approach does not rely on the
integrable character of the model, and indicates how to extend previous results
to any order in powers of . Moreover, the same effective theory can also
be used to describe an entire universality class of -dimensional
fermionic systems beyond the Calogero-Sutherland model, that we identify with
the class of {\it chiral Luttinger systems}. We also explain how a systematic
bosonization procedure can be performed using the \winf generators, and
propose this algebraic approach to {\it classify} low-dimensional
non-relativistic fermionic systems, given that all representations of \winf
are known. This approach has the appeal of being mathematically complete and
physically intuitive, encoding the picture suggested by Luttinger's theorem.Comment: 13 pages, plain LaTeX, no figures
Stable non-BPS D-branes of type I
We review the boundary state description of the non-BPS D-branes in the type
I string theory and show that the only stable configurations are the D-particle
and the D-instanton. We also compute the gauge and gravitational interactions
of the non-BPS D-particles and compare them with the interactions of the dual
non-BPS particles of the heterotic string finding complete agreement. In this
way we provide further dynamical evidence of the heterotic/type I duality.Comment: 8 pages, 1 figure.eps, JHEP.cls, talk given by A. Lerda at the TMR
Conference "Quantum aspects of gauge theories, supersymmetry and
unification", Paris, September 199
The extended conformal theory of Luttinger systems
We describe the recently introduced method of algebraic bosonization of the
-dimensional Luttinger systems by discussing in detail the specific case
of the Calogero-Sutherland model, and mentioning the hard-core Bose gas. We
also compare our findings with the exact Bethe Ansatz results.Comment: 9 pages, plain Latex file, ,based on a talk given by S. Sciuto at the
II International Sakharov Conference on Physics, Moscow, Russia, 20-24 May 9
Anyonic Realization of the Quantum Affine Lie Algebra U_q(A_N)
We give a realization of quantum affine Lie algebra in
terms of anyons defined on a two-dimensional lattice, the deformation parameter
being related to the statistical parameter of the anyons by . In the limit of the deformation parameter going to one we recover
the Feingold-Frenkel fermionic construction of undeformed affine Lie algebra.Comment: 13p LaTeX Document (should be run twice
Gauge theory renormalizations from the open bosonic string
We present a unified point of view on the different methods available in the
literature to extract gauge theory renormalization constants from the
low-energy limit of string theory. The Bern-Kosower method, based on an
off-shell continuation of string theory amplitudes, and the construction of
low-energy string theory effective actions for gauge particles, can both be
understood in terms of strings interacting with background gauge fields, and
thus reproduce, in the low-energy limit, the field theory results of the
background field method. We present in particular a consistent off-shell
continuation of the one-loop gluon amplitudes in the open bosonic string that
reproduces exactly the results of the background field method in the Feynman
gauge.Comment: 14 pages, latex, no figure
Modular anomaly equation, heat kernel and S-duality in N=2 theories
We investigate epsilon-deformed N=2 superconformal gauge theories in four
dimensions, focusing on the N=2* and Nf=4 SU(2) cases. We show how the modular
anomaly equation obeyed by the deformed prepotential can be efficiently used to
derive its non-perturbative expression starting from the perturbative one. We
also show that the modular anomaly equation implies that S-duality is
implemented by means of an exact Fourier transform even for arbitrary values of
the deformation parameters, and then we argue that it is possible,
perturbatively in the deformation, to choose appropriate variables such that it
reduces to a Legendre transform.Comment: 30 pages, LeTeX2e. V2: references added, appendix B expanded, a few
typos correcte
The extended conformal theory of the Calogero-Sutherland model
We describe the recently introduced method of Algebraic Bosonization of
(1+1)-dimensional fermionic systems by discussing the specific case of the
Calogero-Sutherland model. A comparison with the Bethe Ansatz results is also
presented.Comment: 12 pages, plain LaTeX, no figures; To appear in the proceedings of
the IV Meeting "Common Trends in Condensed Matter and High Energy Physics",
Chia Laguna, Cagliari, Italy, 3-10 Sep. 199
Stable non-BPS states in string theory: a pedagogical review
We present a pedagogical review of the stable non-BPS states in string theory
which have recently attracted some attention in the literature. In particular,
following the analysis of A. Sen, we discuss in detail the case of the stable
non-BPS D-particle of Type I theory whose existence is predicted (and required)
by the heterotic/Type I duality. We show that this D-particle originates from
an unstable bound state formed by a D1/anti-D1 pair of Type IIB in which the
tachyon field acquires a solitonic kink configuration. The mechanism of tachyon
condensation is discussed first at a qualitative level and then with an exact
conformal field theory analysis.Comment: 58 pages, 1 figure; minor correction
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