1,913 research outputs found
Loop Variables and Gauge Invariance in (Open) Bosonic String Theory
We give a simplified and more complete description of the loop variable
approach for writing down gauge invariant equations of motion for the fields of
the open string. A simple proof of gauge invariance to all orders is given. In
terms of loop variables, the interacting equations look exactly like the free
equations, but with a loop variable depending on an extra parameter, thus
making it a band of finite width. The arguments for gauge invariance work
exactly as in the free case. We show that these equations are Wilsonian RG
equations with a finite world-sheet cutoff and that in the infrared limit,
equivalence with the Callan-Symanzik -functions should ensure that they
reproduce the on-shell scattering amplitudes in string theory. It is applied to
the tachyon-photon system and the general arguments for gauge invariance can be
easily checked to the order calculated. One can see that when there is a finite
world sheet cutoff in place, even the U(1) invariance of the equations for the
photon, involves massive mode contributions. A field redefinition involving the
tachyon is required to get the gauge transformations of the photon into
standard form.Comment: 20 pages, Late
Loop Variables with Chan-Paton Factors
The Loop Variable method that has been developed for the U(1) bosonic open
string is generalized to include non-Abelian gauge invariance by incorporating
"Chan-Paton" gauge group indices. The scale transformation symmetry that was responsible for gauge invariance in the U(1) case
continues to be a symmetry. In addition there is a "rotation" symmetry. Both
symmetries crucially involve the massive modes. However it is plausible that
only a linear combination, which is the usual Yang-Mills transformation on
massless fields, has a smooth (world sheet) continuum limit. We also illustrate
how an infinite number of terms in the equation of motion in the cutoff theory
add up to give a term that has a smooth continuum limit, and thus contributes
to the low energy Yang-Mills equation of motion.Comment: One paragraph has been modified and the connection with the
Renormalization Group is explaine
Holomorphic Factorization and Renormalization Group in Closed String Theory
The prescription of Kawai, Lewellen and Tye for writing the closed string
tree amplitudes as sums of products of open string tree amplitudes, is applied
to the world sheet renormalization group equation. The main point is that
regularization of the Minkowski (rather than Euclidean) world sheet theory
allows factorization into left-moving and right-moving sectors to be
maintained. Explicit calculations are done for the tachyon and the
(gauge-fixed) graviton.Comment: 19 pages, Latex File, 9 figure
Exact C=1 Boundary Conformal Field Theories
We present a solution of the problem of a free massless scalar field on the
half line interacting through a periodic potential on the boundary. For a
critical value of the period, this system is a conformal field theory with a
non-trivial and explicitly calculable S-matrix for scattering from the
boundary. Unlike all other exactly solvable conformal field theories, it is
non-rational ({\it i.e.} has infinitely many primary fields). It describes the
critical behavior of a number of condensed matter systems, including
dissipative quantum mechanics and of barriers in ``quantum wires''.Comment: harvmac, 10 pages, PUPT-1432/IASSNS-HEP-93/7
Topological-charge anomalies in supersymmetric theories with domain walls
Domain walls in 1+2 dimensions are studied to clarify some general features
of topological-charge anomalies in supersymmetric theories, by extensive use of
a superfield supercurrent. For domain walls quantum modifications of the
supercharge algebra arise not only from the short-distance anomaly but also
from another source of long-distance origin, induced spin in the domain-wall
background, and the latter dominates in the sum. A close look into the
supersymmetric trace identity, which naturally accommodates the central-charge
anomaly and its superpartners, shows an interesting consequence of the
improvement of the supercurrent: Via an improvement the anomaly in the central
charge can be transferred from induced spin in the fermion sector to an induced
potential in the boson sector. This fact reveals a dual character, both
fermionic and bosonic, of the central-charge anomaly, which reflects the
underlying supersymmetry. The one-loop superfield effective action is also
constructed to verify the anomaly and BPS saturation of the domain-wall
spectrum.Comment: 8 pages, Revte
Dynamics of Extremal Black Holes
Particle scattering and radiation by a magnetically charged, dilatonic black
hole is investigated near the extremal limit at which the mass is a constant
times the charge. Near this limit a neighborhood of the horizon of the black
hole is closely approximated by a trivial product of a two-dimensional black
hole with a sphere. This is shown to imply that the scattering of
long-wavelength particles can be described by a (previously analyzed)
two-dimensional effective field theory, and is related to the
formation/evaporation of two-dimensional black holes. The scattering proceeds
via particle capture followed by Hawking re-emission, and naively appears to
violate unitarity. However this conclusion can be altered when the effects of
backreaction are included. Particle-hole scattering is discussed in the light
of a recent analysis of the two-dimensional backreaction problem. It is argued
that the quantum mechanical possibility of scattering off of extremal black
holes implies the potential existence of additional quantum numbers - referred
to as ``quantum whiskers'' - characterizing the black hole.Comment: 31 page
Kaluza-Klein Black Holes in String Theory
Exact solutions of heterotic string theory corresponding to four-dimensional
magnetic black holes in supergravity are described. The solutions
describe the black holes in the throat limit, and consist of a tensor product
of an WZW orbifold with the linear dilaton vacuum, supersymmetrized to
world sheet SUSY. One dimension of the model is interpreted as
a compactified fifth dimension, leading to a four dimensional solution with a
Kaluza-Klein gauge field having a magnetic monopole background; this
corresponds to a solution in supergravity, since that theory is obtained
by dimensional reduction of string theory.Comment: 13p. uses Harvma
Classical moduli hair
We extend existing treatments of black hole solutions in String Gravity to
include moduli fields. We compute the external moduli and dilaton hair, as well
as of their associated axions,to in the framework of the loop
corrected superstring effective action for a Kerr-Newman black hole background.Comment: 11 pages,LaTex file,no figure
Ultra-violet Behavior of Bosonic Quantum Membranes
We treat the action for a bosonic membrane as a sigma model, and then compute
quantum corrections by integrating out higher membrane modes. As in string
theory, where the equations of motion of Einstein's theory emerges by setting
, we find that, with certain assumptions, we can recover the
equations of motion for the background fields. Although the membrane theory is
non-renormalizable on the world volume by power counting, the investigation of
the ultra-violet behavior of membranes may give us insight into the
supersymmetric case, where we hope to obtain higher order M-theory corrections
to 11 dimensional supergravity.Comment: 25 pages, Latex, no figure
Gravitational Radiation from Travelling Waves on D-Strings
Boundary states that preserve supersymmetry are constructed for fractional
D-strings with travelling waves on a
orbifold. The gravitational radiation emitted between two D-strings with
antiparallel travelling waves is calculated.Comment: improvements and correction
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