10 research outputs found
Homothetic perfect fluid space-times
A brief summary of results on homotheties in General Relativity is given,
including general information about space-times admitting an r-parameter group
of homothetic transformations for r>2, as well as some specific results on
perfect fluids. Attention is then focussed on inhomogeneous models, in
particular on those with a homothetic group (acting multiply
transitively) and . A classification of all possible Lie algebra
structures along with (local) coordinate expressions for the metric and
homothetic vectors is then provided (irrespectively of the matter content), and
some new perfect fluid solutions are given and briefly discussed.Comment: 27 pages, Latex file, Submitted to Class. Quantum Gra
BGWM as Second Constituent of Complex Matrix Model
Earlier we explained that partition functions of various matrix models can be
constructed from that of the cubic Kontsevich model, which, therefore, becomes
a basic elementary building block in "M-theory" of matrix models. However, the
less topical complex matrix model appeared to be an exception: its
decomposition involved not only the Kontsevich tau-function but also another
constituent, which we now identify as the Brezin-Gross-Witten (BGW) partition
function. The BGW tau-function can be represented either as a generating
function of all unitary-matrix integrals or as a Kontsevich-Penner model with
potential 1/X (instead of X^3 in the cubic Kontsevich model).Comment: 42 page
Integrability properties of Hurwitz partition functions. II. Multiplication of cut-and-join operators and WDVV equations
Correlators in topological theories are given by the values of a linear form
on the products of operators from a commutative associative algebra (CAA). As a
corollary, partition functions of topological theory always satisfy the
generalized WDVV equations. We consider the Hurwitz partition functions,
associated in this way with the CAA of cut-and-join operators. The ordinary
Hurwitz numbers for a given number of sheets in the covering provide trivial
(sums of exponentials) solutions to the WDVV equations, with finite number of
time-variables. The generalized Hurwitz numbers from arXiv:0904.4227 provide a
non-trivial solution with infinite number of times. The simplest solution of
this type is associated with a subring, generated by the dilatation operators
tr X(d/dX).Comment: 24 page