65,131 research outputs found
A New Family of Solvable Self-Dual Lie Algebras
A family of solvable self-dual Lie algebras is presented. There exist a few
methods for the construction of non-reductive self-dual Lie algebras: an
orthogonal direct product, a double-extension of an Abelian algebra, and a
Wigner contraction. It is shown that the presented algebras cannot be obtained
by these methods.Comment: LaTeX, 12 page
Models for unitary black hole disintegration
Simple models for unitary black hole evolution are given in an effective
Hilbert-space description, parameterizing a possible minimal relaxation of
locality, with respect to semiclassical black hole geometry.Comment: 7 pages of text, plus refs. v2: minor rev
Heterotic Anomaly Cancellation in Five Dimensions
We study the constraints on five-dimensional N=1 heterotic M-theory imposed
by a consistent anomaly-free coupling of bulk and boundary theory. This
requires analyzing the cancellation of triangle gauge anomalies on the
four-dimensional orbifold planes due to anomaly inflow from the bulk. We find
that the semi-simple part of the orbifold gauge groups and certain U(1)
symmetries have to be free of quantum anomalies. In addition there can be
several anomalous U(1) symmetries on each orbifold plane whose anomalies are
cancelled by a non-trivial variation of the bulk vector fields. The mixed U(1)
non-abelian anomaly is universal and there is at most one U(1) symmetry with
such an anomaly on each plane. In an alternative approach, we also analyze the
coupling of five-dimensional gauged supergravity to orbifold gauge theories. We
find a somewhat generalized structure of anomaly cancellation in this case
which allows, for example, non-universal mixed U(1) gauge anomalies. Anomaly
cancellation from the perspective of four-dimensional N=1 effective actions
obtained from E_8xE_8 heterotic string- or M-theory by reduction on a
Calabi-Yau three-fold is studied as well. The results are consistent with the
ones found for five-dimensional heterotic M-theory. Finally, we consider some
related issues of phenomenological interest such as model building with
anomalous U(1) symmetries, Fayet-Illiopoulos terms and threshold corrections to
gauge kinetic functions.Comment: 46 pages, Late
The Structure of Conserved Charges in Open Spin Chains
We study the local conserved charges in integrable spin chains of the XYZ
type with nontrivial boundary conditions. The general structure of these
charges consists of a bulk part, whose density is identical to that of a
periodic chain, and a boundary part. In contrast with the periodic case, only
charges corresponding to interactions of even number of spins exist for the
open chain. Hence, there are half as many charges in the open case as in the
closed case. For the open spin-1/2 XY chain, we derive the explicit expressions
of all the charges. For the open spin-1/2 XXX chain, several lowest order
charges are presented and a general method of obtaining the boundary terms is
indicated. In contrast with the closed case, the XXX charges cannot be
described in terms of a Catalan tree pattern.Comment: 22 pages, harvmac.tex (minor clarifications and reference corrections
added
QED in the worldline representation
Simultaneously with inventing the modern relativistic formalism of quantum
electrodynamics, Feynman presented also a first-quantized representation of QED
in terms of worldline path integrals. Although this alternative formulation has
been studied over the years by many authors, only during the last fifteen years
it has acquired some popularity as a computational tool. I will shortly review
here three very different techniques which have been developed during the last
few years for the evaluation of worldline path integrals, namely (i) the
``string-inspired formalism'', based on the use of worldline Green functions,
(ii) the numerical ``worldline Monte Carlo formalism'', and (iii) the
semiclassical ``worldline instanton'' approach.Comment: 18 pages, 7 figures, talk given at VI Latinamerican Symposium on High
Energy Physics, Nov. 1-8, 2006, Puerto Vallarta, Mexico; references added and
corrected (no other changes
Doubly-Fluctuating BPS Solutions in Six Dimensions
We analyze the BPS solutions of minimal supergravity coupled to an
anti-self-dual tensor multiplet in six dimensions and find solutions that
fluctuate non-trivially as a function of two variables. We consider families of
solutions coming from KKM monopoles fibered over Gibbons-Hawking metrics or,
equivalently, non-trivial T^2 fibrations over an R3 base. We find smooth
microstate geometries that depend upon many functions of one variable, but each
such function depends upon a different direction inside the T^2 so that the
complete solution depends non-trivially upon the whole T^2 . We comment on the
implications of our results for the construction of a general superstratum.Comment: 24 page
Root systems from Toric Calabi-Yau Geometry. Towards new algebraic structures and symmetries in physics?
The algebraic approach to the construction of the reflexive polyhedra that
yield Calabi-Yau spaces in three or more complex dimensions with K3 fibres
reveals graphs that include and generalize the Dynkin diagrams associated with
gauge symmetries. In this work we continue to study the structure of graphs
obtained from reflexive polyhedra. We show how some particularly defined
integral matrices can be assigned to these diagrams. This family of matrices
and its associated graphs may be obtained by relaxing the restrictions on the
individual entries of the generalized Cartan matrices associated with the
Dynkin diagrams that characterize Cartan-Lie and affine Kac-Moody algebras.
These graphs keep however the affine structure, as it was in Kac-Moody Dynkin
diagrams. We presented a possible root structure for some simple cases. We
conjecture that these generalized graphs and associated link matrices may
characterize generalizations of these algebras.Comment: 24 pages, 6 figure
A Solution to the Lorentzian Quantum Reality Problem
The quantum reality problem is that of finding a mathematically precise
definition of a sample space of configurations of beables, events, histories,
paths, or other mathematical objects, and a corresponding probability
distribution, for any given closed quantum system. Given a solution, we can
postulate that physical reality is described by one randomly chosen
configuration drawn from the sample space. For a physically sensible solution,
this postulate should imply quasiclassical physics in realistic models. In
particular, it should imply the validity of Copenhagen quantum theory and
classical dynamics in their respective domains. A Lorentzian solution applies
to relativistic quantum theory or quantum field theory in Minkowski space and
is defined in a way that respects Lorentz symmetry. We outline a new solution
to the non-relativistic and Lorentzian quantum reality problems, and associated
new generalizations of quantum theory
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