2,808 research outputs found
N=1 Super QCD and Fractional Branes
We show how to get the one-loop beta function and the chiral anomaly of N=1
Super QCD from a stack of fractional N D3-branes localized inside the
world-volume of 2M fractional D7-branes on the orbifold C^3/(Z_2 x Z_2). They
are obtained by analyzing the classical supergravity background generated by
such a brane configuration, in the spirit of the gauge/gravity correspondence.Comment: 4 pages, LaTeX. Talk given at the IXth International Symposium on
Particles, Strings and Cosmology PASCOS '03, Mumbai-India, January 3-8 2003.
To appear in a special issue of Praman
N=2 four-dimensional gauge theories from fractional branes
This is a pedagogical and extended version of the results published in Refs.
[1,2] and presented by the authors in various talks during the last year. We
discuss the type II D-branes (both regular and fractional) of the orbifold
R^{1,5}*R^4/Z_2, we determine their corresponding supergravity solution and
show how this can be used to study the properties of N=2 super Yang-Mills.
Supergravity is able to reproduce the perturbative moduli space of the gauge
theory, while it does not encode the non-perturbative corrections. The short
distance region of space-time, which corresponds to the infrared region of the
gauge theory, is excised by an enhancon mechanism, and more states should be
included in the low energy effective action in order to enter inside the
enhancon and recover the instanton corrections. (To be published on a Memorial
Volume commemorating Michael Marinov)Comment: 44 pages, AMS-LaTeX, no figure
Non-perturbative effective model for the Higgs sector of the Standard Model
A non-perturbative effective model is derived for the Higgs sector of the
standard model, described by a simple scalar theory. The renormalized couplings
are determined by the derivatives of the Gaussian Effective Potential that are
known to be the sum of infinite bubble graphs contributing to the vertex
functions. A good agreement has been found with strong coupling lattice
simulations when a comparison can be made
Fractional Branes and N=1 Gauge Theories
We discuss fractional D3-branes on the orbifold C^3/Z_2*Z_2. We study the
open and the closed string spectrum on this orbifold. The corresponding N=1
theory on the brane has, generically, a U(N_1)*U(N_2)*U(N_3)*U(N_4) gauge group
with matter in the bifundamental. In particular, when only one type of brane is
present, one obtains pure N=1 Yang-Mills. We study the coupling of the branes
to the bulk fields and present the corresponding supergravity solution, valid
at large distances. By using a probe analysis, we are able to obtain the
Wilsonian beta-function for those gauge theories that possess some chiral
multiplet. Although, due to the lack of moduli, the probe technique is not
directly applicable to the case of pure N=1 Yang-Mills, we point out that the
same formula gives the correct result also for this case.Comment: 21 pages, AMS-LaTeX, v2: references added and typos correcte
Anomalies and Tadpoles in Open/Closed String Duality
We discuss the role played by the divergences appearing in the interaction
between a fractional D3 brane dressed with an SU(N) gauge field and a stack of
N fractional D3 branes on the orbifolds C^2/Z_2 and C^3/(Z_2 x Z_2). In
particular we show that the logarithmic divergences in the closed string
channel, interpreted as due to twisted massless tadpoles, are mapped, under
open/closed string duality, in the logarithmic ones in the open string channel,
due to the massless states circulating in the annulus diagram and corresponding
to the one-loop divergences that one finds in the gauge theory living in the
world volume of the brane. This result provides a quantitative evidence of why
the chiral and scale anomalies of the supersymmetric and non conformal gauge
theories supported by the world volume of the branes can be inferred from
supergravity calculations.Comment: LaTeX, 8 pages. Contribution to the proceedings of the workshop of
the RTN Network "The quantum structure of space-time and the geometric nature
of fundamental interactions", Copenhagen, September 200
Singular perturbations of zâż with a pole on the unit circle
We consider the family of complex maps given by fλ,a (z) = z n + λ/(z â a)d where n, d â„ 1 are integers, and a and λ are complex parameters such that a = 1 and is sufficiently small. We focus on the topological characteristics of the Julia and Fatou sets of fλ,a
Topological order in Josephson junction ladders with Mobius boundary conditions
We propose a CFT description for a closed one-dimensional fully frustrated
ladder of quantum Josephson junctions with Mobius boundary conditions, in
particular we show how such a system can develop topological order. Such a
property is crucial for its implementation as a "protected" solid state qubit.Comment: 14 pages, 3 figures, to appear in JSTA
Brane-Inspired Orientifold Field Theories
In this paper we consider the gauge theory living on the world-volume of a
stack of N D3-branes of Type 0B/\Omega' I_6(-1)^{F_{L}} and of its orbifolds
C^2/Z_2 and C^3/(Z_2 x Z_2). The gauge theories obtained in the three cases are
a brane realization of ``orientifold field theories'' having the bosonic sector
common with N=4,2,1 super Yang-Mills respectively. In these non-supersymmetric
theories, we investigate the possibility of keeping the gauge/gravity
correspondence that has revealed itself so successful in the case of
supersymmetric theories. In the open string framework we compute the
coefficient of the gauge kinetic term showing that the perturbative behaviour
of the orientifold field theory can be obtained from the closed string channel
in the large N limit, where the theory exhibits Bose-Fermi degeneracy.Comment: 27 pages, LaTe
- âŠ