27,444 research outputs found
Deformations of quantum field theories and integrable models
Deformations of quantum field theories which preserve Poincar\'e covariance
and localization in wedges are a novel tool in the analysis and construction of
model theories. Here a general scenario for such deformations is discussed, and
an infinite class of explicit examples is constructed on the Borchers-Uhlmann
algebra underlying Wightman quantum field theory. These deformations exist
independently of the space-time dimension, and contain the recently studied
warped convolution deformation as a special case. In the special case of
two-dimensional Minkowski space, they can be used to deform free field theories
to integrable models with non-trivial S-matrix.Comment: 36 pages, no figures: Minor changes and corrections in Section 3.
Added new Section 5 on von Neumann algebraic formulation, and modular
structur
Holographic c-theorems in arbitrary dimensions
We re-examine holographic versions of the c-theorem and entanglement entropy
in the context of higher curvature gravity and the AdS/CFT correspondence. We
select the gravity theories by tuning the gravitational couplings to eliminate
non-unitary operators in the boundary theory and demonstrate that all of these
theories obey a holographic c-theorem. In cases where the dual CFT is
even-dimensional, we show that the quantity that flows is the central charge
associated with the A-type trace anomaly. Here, unlike in conventional
holographic constructions with Einstein gravity, we are able to distinguish
this quantity from other central charges or the leading coefficient in the
entropy density of a thermal bath. In general, we are also able to identify
this quantity with the coefficient of a universal contribution to the
entanglement entropy in a particular construction. Our results suggest that
these coefficients appearing in entanglement entropy play the role of central
charges in odd-dimensional CFT's. We conjecture a new c-theorem on the space of
odd-dimensional field theories, which extends Cardy's proposal for even
dimensions. Beyond holography, we were able to show that for any
even-dimensional CFT, the universal coefficient appearing the entanglement
entropy which we calculate is precisely the A-type central charge.Comment: 62 pages, 4 figures, few typo's correcte
Nonuniversality in quantum wires with off-diagonal disorder: a geometric point of view
It is shown that, in the scaling regime, transport properties of quantum
wires with off-diagonal disorder are described by a family of scaling equations
that depend on two parameters: the mean free path and an additional continuous
parameter. The existing scaling equation for quantum wires with off-diagonal
disorder [Brouwer et al., Phys. Rev. Lett. 81, 862 (1998)] is a special point
in this family. Both parameters depend on the details of the microscopic model.
Since there are two parameters involved, instead of only one, localization in a
wire with off-diagonal disorder is not universal. We take a geometric point of
view and show that this nonuniversality follows from the fact that the group of
transfer matrices is not semi-simple. Our results are illustrated with
numerical simulations for a tight-binding model with random hopping amplitudes.Comment: 12 pages, RevTeX; 3 figures included with eps
Combinatorial quantization of the Hamiltonian Chern-Simons theory I
Motivated by a recent paper of Fock and Rosly \cite{FoRo} we describe a
mathematically precise quantization of the Hamiltonian Chern-Simons theory. We
introduce the Chern-Simons theory on the lattice which is expected to reproduce
the results of the continuous theory exactly. The lattice model enjoys the
symmetry with respect to a quantum gauge group. Using this fact we construct
the algebra of observables of the Hamiltonian Chern-Simons theory equipped with
a *-operation and a positive inner product.Comment: 49 pages. Some minor corrections, discussion of positivity improved,
a number of remarks and a reference added
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