4,350 research outputs found
On the classification of quantum W-algebras
In this paper we consider the structure of general quantum W-algebras. We
introduce the notions of deformability, positive-definiteness, and reductivity
of a W-algebra. We show that one can associate a reductive finite Lie algebra
to each reductive W-algebra. The finite Lie algebra is also endowed with a
preferred subalgebra, which gives the conformal weights of the
W-algebra. We extend this to cover W-algebras containing both bosonic and
fermionic fields, and illustrate our ideas with the Poisson bracket algebras of
generalised Drinfeld-Sokolov Hamiltonian systems. We then discuss the
possibilities of classifying deformable W-algebras which fall outside this
class in the context of automorphisms of Lie algebras. In conclusion we list
the cases in which the W-algebra has no weight one fields, and further, those
in which it has only one weight two field.Comment: 28 page
Purely transmitting integrable defects
Some aspects of integrable field theories possessing purely transmitting
defects are described. The main example is the sine-Gordon model and several
striking features of a classical field theory containing one or more defects
are pointed out. Similar features appearing in the associated quantum field
theory are also reviewed briefly.Comment: 6 pages, to appear in Proceedings of the XVth International
Colloquium on Integrable Systems and Quantum Symmetries, Prague, June 200
Integrable Field Theories with Defects
The structure of integrable field theories in the presence of defects is
discussed in terms of boundary functions under the Lagrangian formalism.
Explicit examples of bosonic and fermionic theories are considered. In
particular, the boundary functions for the super sinh-Gordon model is
constructed and shown to generate the Backlund transformations for its soliton
solutions.Comment: talk presented at the XVth International Colloquium on Integrable
Systems and Quantum Symmetries, to appear in Czechoslovak Journal of Physics
(2006
Comment on 4D Lorentz invariance violations in the brane-world
The brane-world scenario offers the possibility for signals to travel outside
our visible universe and reenter it. We find the condition for a signal emitted
from the brane to return to the brane. We study the propagation of such signals
and show that, as seen by a 4D observer, these signals arrive earlier than
light traveling along the brane. We also study the horizon problem and find
that, while the bulk signals can travel far enough to homogenize the visible
universe, it is unlikely that they have a significant effect since they are
redshifted in the gravitational field of the bulk black hole.Comment: 21 pages, 6 figures, REVTEX, New section adde
Null vectors, 3-point and 4-point functions in conformal field theory
We consider 3-point and 4-point correlation functions in a conformal field
theory with a W-algebra symmetry. Whereas in a theory with only Virasoro
symmetry the three point functions of descendants fields are uniquely
determined by the three point function of the corresponding primary fields this
is not the case for a theory with algebra symmetry. The generic 3-point
functions of W-descendant fields have a countable degree of arbitrariness. We
find, however, that if one of the fields belongs to a representation with null
states that this has implications for the 3-point functions. In particular if
one of the representations is doubly-degenerate then the 3-point function is
determined up to an overall constant. We extend our analysis to 4-point
functions and find that if two of the W-primary fields are doubly degenerate
then the intermediate channels are limited to a finite set and that the
corresponding chiral blocks are determined up to an overall constant. This
corresponds to the existence of a linear differential equation for the chiral
blocks with two completely degenerate fields as has been found in the work of
Bajnok~et~al.Comment: 10 pages, LaTeX 2.09, DAMTP-93-4
Brane-world generalizations of the Einstein static universe
A static Friedmann brane in a 5-dimensional bulk (Randall-Sundrum type
scenario) can have a very different relation between the density, pressure,
curvature and cosmological constant than in the case of the general
relativistic Einstein static universe. In particular, static Friedmann branes
with zero cosmological constant and 3-curvature, but satisfying rho>0 and
rho+3p>0, are possible. Furthermore, we find static Friedmann branes in a bulk
that satisfies the Einstein equations but is not Schwarzschild-anti de Sitter
or its specializations. In the models with negative bulk cosmological constant,
a positive brane tension leads to negative density and 3-curvature.Comment: additional interpretation of new solutions; accepted by
Class.Quant.Gra
Physics Opportunities with the FCC-hh Injectors
In this chapter we explore a few examples of physics opportunities using the
existing chain of accelerators at CERN, including potential upgrades. In this
context the LHC ring is also considered as a part of the injector system. The
objective is to find examples that constitute sensitive probes of New Physics
that ideally cannot be done elsewhere or can be done significantly better at
theCERN accelerator complex. Some of these physics opportunities may require a
more flexible injector complex with additional functionality than that just
needed to inject protons into the FCC-hh at the right energy, intensity and
bunch structure. Therefore it is timely to discuss these options concurrently
with the conceptual design of the FCC-hh injector system.Comment: 13 pages, chapter 5 in Physics at the FCC-hh, a 100 TeV pp collide
The sine-Gordon model with integrable defects revisited
Application of our algebraic approach to Liouville integrable defects is
proposed for the sine-Gordon model. Integrability of the model is ensured by
the underlying classical r-matrix algebra. The first local integrals of motion
are identified together with the corresponding Lax pairs. Continuity conditions
imposed on the time components of the entailed Lax pairs give rise to the
sewing conditions on the defect point consistent with Liouville integrability.Comment: 24 pages Latex. Minor modifications, added comment
Gravitating global defects: the gravitational field and compactification
We give a prescription to add the gravitational field of a global topological
defect to a solution of Einstein's equations in an arbitrary number of
dimensions. We only demand that the original solution has a O(n) invariance
with n greater or equal 3. We will see that the general effect of a global
defect is to introduce a deficit solid angle. We also show how the same kind of
scalar field configurations can be used for spontaneous compactification of "n"
extra dimensions on an n-sphere.Comment: Uses revte
Dyonic Giant Magnons
We study the classical spectrum of string theory on AdS_5 X S^5 in the
Hofman-Maldacena limit. We find a family of classical solutions corresponding
to Giant Magnons with two independent angular momenta on S^5. These solutions
are related via Pohlmeyer's reduction procedure to the charged solitons of the
Complex sine-Gordon equation. The corresponding string states are dual to BPS
boundstates of many magnons in the spin-chain description of planar N=4 SUSY
Yang-Mills. The exact dispersion relation for these states is obtained from a
purely classical calculation in string theory.Comment: LaTeX file, 16 pages. One figure. Corrected reference
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