7,211 research outputs found
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 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 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 case. Finally we
analyze the vacuum structure of the 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
Some Global Aspects of Duality is String Theory
We explore some of the global aspects of duality transformations in String
Theory and Field Theory. We analyze in some detail the equivalence of dual
models corresponding to different topologies at the level of the partition
function and in terms of the operator correspondence for abelian duality. We
analyze the behavior of the cosmological constant under these transformations.
We also explore several examples of non-abelian duality where the classical
background interpretation can be maintained for the original and the dual
theories. In particular we construct a non-abelian dual of which
turns out to be a three-dimensional black holeComment: 31pp. One figure available upon request. CERN-TH-6991/6
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.
-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
Comments on Noncommutative Field Theories
We discuss some aspects of noncommutative quantum field theories obtained
from the Seiberg-Witten limit of string theories in the presence of an external
B-field. General properties of these theories are studied as well as the
phenomenological potential of noncommutative QED.Comment: 15 pages. Based on talks at the 9th Adriatic Meeting (Dubrovnik,
Croatia) and at String Phenomenology 2003 (Durham, UK). v2 references adde
Remarks on Time-Space Noncommutative Field Theories
We propose a physical interpretation of the perturbative breakdown of
unitarity in time-like noncommutative field theories in terms of production of
tachyonic particles. These particles may be viewed as a remnant of a continuous
spectrum of undecoupled closed-string modes. In this way, we give a unified
view of the string-theoretical and the field-theoretical no-go arguments
against time-like noncommutative theories. We also perform a quantitative study
of various locality and causality properties of noncommutative field theories
at the quantum level.Comment: 19 pages, LaTe
Domain Wall Fermions and the Eta Invariant
We extend work by Callan and Harvey and show how the phase of the chiral
fermion determinant in four dimensions is reproduced by zeromodes bound to a
domain wall in five dimensions. The analysis could shed light on the
applicability of zeromode fermions and the vacuum overlap formulation of
Narayanan and Neuberger for chiral gauge theories on the lattice.Comment: uuencoded file with 3 figures; uses macros harvmac, epsf. Revised
discussion of the Chern-Simons form and SU(2) anomaly in section 4, as well
as additional minor change
Nonperturbative Solution of the Super-Virasoro Constraints
We present the solution of the discrete super-Virasoro constraints to all
orders of the genus expansion. Integrating over the fermionic variables we get
a representation of the partition function in terms of the one-matrix model. We
also obtain the nonperturbative solution of the super-Virasoro constraints in
the double scaling limit but do not find agreement between our flows and the
known supersymmetric extensions of KdV.Comment: 12 pages, CERN-TH.6761/9
Non-Abelian Duality and Canonical Transformations
We construct explicit canonical transformations producing non-abelian duals
in principal chiral models with arbitrary group G. Some comments concerning the
extension to more general -models, like WZW models, are given.Comment: 9 pags, latex fil
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