1,661 research outputs found
Simple currents versus orbifolds with discrete torsion -- a complete classification
We give a complete classification of all simple current modular invariants,
extending previous results for (\Zbf_p)^k to arbitrary centers. We obtain a
simple explicit formula for the most general case. Using orbifold techniques to
this end, we find a one-to-one correspondence between simple current invariants
and subgroups of the center with discrete torsions. As a by-product, we prove
the conjectured monodromy independence of the total number of such invariants.
The orbifold approach works in a straightforward way for symmetries of odd
order, but some modifications are required to deal with symmetries of even
order. With these modifications the orbifold construction with discrete torsion
is complete within the class of simple current invariants. Surprisingly, there
are cases where discrete torsion is a necessity rather than a possibility.Comment: 28 page
Formula for Fixed Point Resolution Matrix of Permutation Orbifolds
We find a formula for the resolution of fixed points in extensions of
permutation orbifold conformal field theories by its (half-)integer spin simple
currents. We show that the formula gives a unitary and modular invariant S
matrix.Comment: 42 page
Permutation Orbifold of N=2 Supersymmetric Minimal Models
In this paper we apply the previously derived formalism of permutation
orbifold conformal field theories to N=2 supersymmetric minimal models. By
interchanging extensions and permutations of the factors we find a very
interesting structure relating various conformal field theories that seems not
to be known in literature. Moreover, unexpected exceptional simple currents
arise in the extended permuted models, coming from off-diagonal fields. In a
few situations they admit fixed points that must be resolved. We determine the
complete CFT data with all fixed point resolution matrices for all simple
currents of all Z_2-permutations orbifolds of all minimal N=2 models with k\neq
2 mod 4.Comment: 48 page
Permutation orbifolds of heterotic Gepner models
We study orbifolds by permutations of two identical N=2 minimal models within
the Gepner construction of four dimensional heterotic strings. This is done
using the new N=2 supersymmetric permutation orbifold building blocks we have
recently developed. We compare our results with the old method of modding out
the full string partition function. The overlap between these two approaches is
surprisingly small, but whenever a comparison can be made we find complete
agreement. The use of permutation building blocks allows us to use the complete
arsenal of simple current techniques that is available for standard Gepner
models, vastly extending what could previously be done for permutation
orbifolds. In particular, we consider (0,2) models, breaking of SO(10) to
subgroups, weight-lifting for the minimal models and B-L lifting. Some
previously observed phenomena, for example concerning family number
quantization, extend to this new class as well, and in the lifted models three
family models occur with abundance comparable to two or four.Comment: 49 pages, 4 figure
(0,2) string compactifications
Using the simple current method we study a class of SCFTs which we
conjecture to be equivalent to (0,2) sigma models constructed in the framework
of gauged linear sigma models.Comment: Talk at the International Symposium on the Theory of Elementary
Particles Buckow, August 27-31, 1996; LaTeX, fleqn.sty, espcrc2.sty; 6 page
Detecting multi-atomic composite states in optical lattices
We propose and discuss methods for detecting quasi-molecular complexes which
are expected to form in strongly interacting optical lattice systems.
Particular emphasis is placed on the detection of composite fermions forming in
Bose-Fermi mixtures. We argue that, as an indirect indication of the composite
fermions and a generic consequence of strong interactions, periodic
correlations must appear in the atom shot noise of bosonic absorption images,
similar to the bosonic Mott insulator [S. F\"olling, et al., Nature {\bf 434},
481 (2005)]. The composites can also be detected directly and their
quasi-momentum distribution measured. This method -- an extension of the
technique of noise correlation interferometry [E. Altman et al., Phys. Rev. A
{\bf 79}, 013603 (2004)] -- relies on measuring higher order correlations
between the bosonic and fermionic shot noise in the absorption images. However,
it fails for complexes consisting of more than three atoms.Comment: 9 revtex page
Fixed Point Resolution in Extensions of Permutation Orbifolds
We determine the simple currents and fixed points of the orbifold theory
, given the simple currents and fixed point of the
original . We see in detail how this works for the WZW model,
focusing on the field content (i.e. -spectrum of the primary fields) of the
theory. We also look at the fixed point resolution of the simple current
extended orbifold theory and determine the matrices associated to each
simple current for and for the and series.Comment: 35 pages, no figure
- …