728 research outputs found

### Duality in Quantum Field Theory (and String Theory)

These lectures give an introduction to duality in Quantum Field Theory. We
discuss the phases of gauge theories and the implications of the
electric-magnetic duality transformation to describe the mechanism of
confinement. We review the exact results of N=1 supersymmetric QCD and the
Seiberg-Witten solution of N=2 super Yang-Mills. Some of its extensions to
String Theory are also briefly discussed.Comment: 38 pages, 7 figures, LaTeX, revtex, two references added. Based on a
lectures delivered by L. A.-G. at `The Workshop on Fundamental Particles and
Interactions', held in Vanderbilt University, and CERN-La Plata-Santiago de
Compostela School of Physics, both in May 199

### De Rham Cohomology of the Supermanifolds and Superstring BRST Cohomology

We show that the BRST operator of Neveu-Schwarz-Ramond superstring is closely
related to de Rham differential on the moduli space of decorated super-Riemann
surfaces P. We develop formalism where superstring amplitudes are computed via
integration of some differential forms over a section of P over the super
moduli space M. We show that the result of integration does not depend on the
choice of section when all the states are BRST physical. Our approach is based
on the geometrical theory of integration on supermanifolds of which we give a
short review.Comment: 6 page

### More On Critical Collapse of Axion-Dilaton System in Dimension Four

We complete our previous study of critical gravitational collapse in the
axion-dilaton system by analysing the hyperbolic and parabolic ans\"atze. As
could be expected, the corresponding Choptuik exponents in four-dimensions
differ from the elliptic case.Comment: 13 pages, Latex file, no figure,v2: to appear in JCA

### Generalized Dirichlet Branes and Zero-modes

We investigate the effective dynamics of an arbitrary Dirichlet p-brane, in a
path-integral formalism, by incorporating the massless excitations of closed
string modes in open bosonic string theory. It is shown that the closed string
background fields in the bosonic sector of type II theories induce invariant
extrinsic curvature on the world-volume. In addition, the curvature can be seen
to be associated with a divergence at the boundary of string world-sheet. The
re-normalization of the collective coordinates, next to leading order in its
derivative expansion, is performed to handle the divergence and the effective
dynamics is encoded in Dirac-Born-Infeld action. Furthermore, the collective
dynamics is generalized to include appropriate fermionic partners in type I
super-string theory. The role of string modes is reviewed in terms of the
collective coordinates and the gauge theory on the world-volume is argued to be
non-local in presence of the U(1) invariant field strength.Comment: LaTex, 20 pages, v2: minor changes and added references v3:typos
corrected, some statements are clarified in the context of zero-mode

### More on softly broken N=2 QCD

We extend previous work on the soft breaking of $N=2$ supersymmetric QCD. We
present the formalism for the breaking due to a dilaton spurion for a general
gauge group and obtain the exact effective potential. We obtain some general
features of the vacuum structure in the pure $SU(N)$ Yang-Mills theory and we
also derive a general mass formula for this class of theories, in particular we
present explicit results for the mass spectrum in the $SU(2)$ case. Finally we
analyze the vacuum structure of the $SU(2)$ theory with one massless
hypermultiplet. This theory presents dyon condensation and a first order phase
transition in the supersymmetry breaking parameter driven by non-mutually local
BPS states. This could be a hint of Argyres-Douglas-like phases in
non-supersymmetric gauge theories.Comment: 35 pages, 9 Postscript figure

### Chiral Determinant as an Overlap of Two Vacua

The effective action induced by chiral fermions can be written, formally, as
an overlap of two states. These states are the Fock ground states of
Hamiltonians for fermions in even dimensional space with opposite sign mass
terms coupled to identical static vector potentials. A perturbative analysis of
the overlap in the continuum framework produces the correct anomaly for Abelian
gauge fields in two dimensions. When a lattice transfer matrix formalism is
applied in the direction perpendicular to a domain wall on which chiral
fermions live a lattice version of the overlap is obtained. The real part of
the overlap is nonperturbatively defined and previous work indicates that the
real part of the vacuum polarization tensor in four dimensions has the correct
continuum limit for a chiral theory. The phase of the overlap represents the
imaginary part of the chiral action and suffers from ambiguities.Comment: 37p

### Beyond the String Genus

In an earlier work we used a path integral analysis to propose a higher genus
generalization of the elliptic genus. We found a cobordism invariant
parametrized by Teichmuller space. Here we simplify the formula and study the
behavior of our invariant under the action of the mapping class group of the
Riemann surface. We find that our invariant is a modular function with
multiplier just as in genus one.Comment: 40 pages, 1 figur

### Topics in String Theory and Quantum Gravity

These are the lecture notes for the Les Houches Summer School on Quantum
Gravity held in July 1992. The notes present some general critical assessment
of other (non-string) approaches to quantum gravity, and a selected set of
topics concerning what we have learned so far about the subject from string
theory. Since these lectures are long (133 A4 pages), we include in this
abstract the table of contents, which should help the user of the bulletin
board in deciding whether to latex and print the full file.
1-FIELD THEORETICAL APPROACH TO QUANTUM GRAVITY: Linearized gravity;
Supergravity; Kaluza-Klein theories; Quantum field theory and classical
gravity; Euclidean approach to Quantum Gravity; Canonical quantization of
gravity; Gravitational Instantons.
2-CONSISTENCY CONDITIONS: ANOMALIES: Generalities about anomalies; Spinors in
2n dimensions; When can we expect to find anomalies?; The Atiyah-Singer Index
Theorem and the computation of anomalies; Examples: Green-Schwarz cancellation
mechanism and Witten's SU(2) global anomaly.
3-STRING THEORY I. BOSONIC STRING: Bosonic string; Conformal Field Theory;
Quantization of the bosonic string; Interaction in string theory and the
characterization of the moduli space; Bosonic strings with background fields.
Stringy corrections to Einstein equations; Toroidal compactifications.
$R$-duality; Operator formalism
4-STRING THEORY II. FERMIONIC STRINGS: Fermionic String; Heterotic String;
Strings at finite temperature; Is string theory finite?
5-OTHER DEVELOPMENTS AND CONCLUSIONS: String ``Phenomenology''; Black Holes
and Related SubjectsComment: 133 pages, 22 figures (not included, available upon request), LaTe

### Initial conditions for inflation and the energy scale of SUSY-breaking from the (nearly) gaussian sky

We show how general initial conditions for small field inflation can be
obtained in multi-field models. This is provided by non-linear angular friction
terms in the inflaton that provide a phase of non-slow-roll inflation before
the slow-roll inflation phase. This in turn provides a natural mechanism to
star small-field slow-roll at nearly zero velocity for arbitrary initial
conditions. We also show that there is a relation between the scale of SUSY
breaking sqrt (f) and the amount of non-gaussian fluctuations generated by the
inflaton. In particular, we show that in the local non-gaussian shape there
exists the relation sqrt (f) = 10^{13} GeV sqrt (f_NL). With current
observational limits from Planck, and adopting the minimum amount of
non-gaussian fluctuations allowed by single-field inflation, this provides a
very tight constraint for the SUSY breaking energy scale sqrt (f) = 3-7 x
10^{13} GeV at 95% confidence. Further limits, or detection, from next year's
Planck polarisation data will further tighten this constraint by a factor of
two. We highlight that the key to our approach is to identify the inflaton with
the scalar component of the goldstino superfield. This superfield is universal
and implements the dynamics of SUSY breaking as well as superconformal
breaking.Comment: Invited talk at the BW2013 meetin

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