803 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
N=2 Instanton Calculus In Closed String Background
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 study a system of fractional D3/D(-1)
branes in a Z_2 orbifold and in a Ramond-Ramond closed string background, and
show that it describes the gauge instantons of N=2 super Yang-Mills theory and
their interactions with the graviphoton of N=2. Using string theory methods we
compute the prepotential of the effective gauge theory exploiting the
localization methods of the instanton calculus, showing that this leads to the
same information given by the topological string.Comment: 12 pages, 2 figures; to appear in the proceedings of 21st
Nishinomiya-Yukawa Memorial Symposium on Theoretical Physics: Noncommutative
Geometry and Quantum Spacetime in Physics, Nishinomiya and Kyoto, Japan,
11-15 Nov 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
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
Fumonisins in Foods from Cordoba (Argentina), Presence: Mini Review
This review emphasizes, specifically, the determination of fumonisins in different food substrates, made in
different commercial centers of CĂłrdoba, Argentina. The importance of reviewing this research is related to public health, since food is part of human development and this must be safe. These contaminations, which we try to determine in different food substrates, in some cases occurred in very small quantities, but in most cases, the
consumption is through the children and for long periods of time. Among these foods are those based on corn, this
cereal has a great possibility of being contaminated with fumonisins and other mycotoxins as evidenced by research
conducted in our country.Fil: Lerda, Daniel Enrique. Universidad CatĂłlica de CĂłrdoba. Facultad de Ciencias de la Salud; Argentin
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
Algebraic bosonization: the study of the Heisenberg and Calogero-Sutherland models
We propose an approach to treat (1+1)--dimensional fermionic systems based on
the idea of algebraic bosonization. This amounts to decompose the elementary
low-lying excitations around the Fermi surface in terms of basic building
blocks which carry a representation of the W_{1+\infty} \times {\overline
W_{1+\infty}} algebra, which is the dynamical symmetry of the Fermi quantum
incompressible fluid. This symmetry simply expresses the local particle-number
current conservation at the Fermi surface. The general approach is illustrated
in detail in two examples: the Heisenberg and Calogero-Sutherland models, which
allow for a comparison with the exact Bethe Ansatz solution.Comment: 51 pages, plain LaTe
Deformed N=2 theories, generalized recursion relations and S-duality
We study the non-perturbative properties of N=2 super conformal field
theories in four dimensions using localization techniques. In particular we
consider SU(2) gauge theories, deformed by a generic epsilon-background, with
four fundamental flavors or with one adjoint hypermultiplet. In both cases we
explicitly compute the first few instanton corrections to the partition
function and the prepotential using Nekrasov's approach. These results allow to
reconstruct exact expressions involving quasi-modular functions of the bare
gauge coupling constant and to show that the prepotential terms satisfy a
modular anomaly equation that takes the form of a recursion relation with an
explicitly epsilon-dependent term. We then investigate the implications of this
recursion relation on the modular properties of the effective theory and find
that with a suitable redefinition of the prepotential and of the effective
coupling it is possible, at least up to the third order in the deformation
parameters, to cast the S-duality relations in the same form as they appear in
the Seiberg-Witten solution of the undeformed theory.Comment: 33 pages, no figures, LaTeX2
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