3,193 research outputs found
Poisson sigma model and semiclassical quantization of integrable systems
In this paper we outline the construction of semiclassical eigenfunctions of
integrable models in terms of the semiclassical path integral for the Poisson
sigma model with the target space being the phase space of the integrable
system. The semiclassical path integral is defined as a formal power series
with coefficients being Feynman diagrams. We also argue that in a similar way
one can obtain irreducible semiclassical representations of Kontsevich's star
product.Comment: 22 pages, 12 figure
On C*-algebras associated to right LCM semigroups
We initiate the study of the internal structure of C*-algebras associated to
a left cancellative semigroup in which any two principal right ideals are
either disjoint or intersect in another principal right ideal; these are
variously called right LCM semigroups or semigroups that satisfy Clifford's
condition. Our main findings are results about uniqueness of the full semigroup
C*-algebra. We build our analysis upon a rich interaction between the group of
units of the semigroup and the family of constructible right ideals. As an
application we identify algebraic conditions on S under which C*(S) is purely
infinite and simple.Comment: 31 page
C*-Algebras of algebraic dynamical systems and right LCM semigroups
We introduce algebraic dynamical systems, which consist of an action of a
right LCM semigroup by injective endomorphisms of a group. To each algebraic
dynamical system we associate a C*-algebra and describe it as a semigroup
C*-algebra. As part of our analysis of these C*-algebras we prove results for
right LCM semigroups. More precisely we discuss functoriality of the full
semigroup C*-algebra and compute its K-theory for a large class of semigroups.
We introduce the notion of a Nica-Toeplitz algebra of a product system over a
right LCM semigroup, and show that it provides a useful alternative to study
algebraic dynamical systems.Comment: 28 pages, to appear in Indiana Univ. Math.
Monodromy Matrix in the PP-Wave Limit
We construct the monodromy matrix for a class of gauged WZWN models in the
plane wave limit and discuss various properties of such systems.Comment: 16 page
Arbitrary Spin Representations in de Sitter from dS/CFT with Applications to dS Supergravity
We present a simple group representation analysis of massive, and
particularly ``partially massless'', fields of arbitrary spin in de Sitter
spaces of any dimension. The method uses bulk to boundary propagators to relate
these fields to Euclidean conformal ones at one dimension lower. These results
are then used to revisit an old question: can a consistent de Sitter
supergravity be constructed, at least within its intrinsic horizon?Comment: 19 pages LaTex, references added, version to appear Nucl. Phys.
AdS vacua and RG flows in three dimensional gauged supergravities
We study supersymmetric vacua in N=4 and N=8, three dimensional
gauged supergravities, with scalar manifolds and , non-semisimple Chern-Simons
gaugings and ,
respectively. These are in turn equivalent to SO(4) and
Yang-Mills theories coupled to supergravity. For the N=4 case, we study
renormalization group flows between UV and IR vacua with the same
amount of supersymmetry: in one case, with (3,1) supersymmetry, we can find an
analytic solution whereas in another, with (2,0) supersymmetry, we give a
numerical solution. In both cases, the flows turn out to be v.e.v. flows, i.e.
they are driven by the expectation value of a relevant operator in the dual
. These provide examples of v.e.v. flows between two vacua
within a gauged supergravity framework.Comment: 35 pages in JHEP form, 3 figures, typos corrected, references adde
Antenna-enhanced Optoelectronic Probing of Carbon Nanotubes
We report on the first antenna-enhanced optoelectronic microscopy studies on
nanoscale devices. By coupling the emission and excitation to a scanning
optical antenna, we are able to locally enhance the electroluminescence and
photocurrent along a carbon nanotube device. We show that the emission source
of the electroluminescence can be point-like with a spatial extension below 20
nm. Topographic and antenna-enhanced photocurrent measurements reveal that the
emission takes place at the location of highest local electric field indicating
that the mechanism behind the emission is the radiative decay of excitons
created via impact excitation
Gradient Representations and Affine Structures in AE(n)
We study the indefinite Kac-Moody algebras AE(n), arising in the reduction of
Einstein's theory from (n+1) space-time dimensions to one (time) dimension, and
their distinguished maximal regular subalgebras sl(n) and affine A_{n-2}^{(1)}.
The interplay between these two subalgebras is used, for n=3, to determine the
commutation relations of the `gradient generators' within AE(3). The low level
truncation of the geodesic sigma-model over the coset space AE(n)/K(AE(n)) is
shown to map to a suitably truncated version of the SL(n)/SO(n) non-linear
sigma-model resulting from the reduction Einstein's equations in (n+1)
dimensions to (1+1) dimensions. A further truncation to diagonal solutions can
be exploited to define a one-to-one correspondence between such solutions, and
null geodesic trajectories on the infinite-dimensional coset space H/K(H),
where H is the (extended) Heisenberg group, and K(H) its maximal compact
subgroup. We clarify the relation between H and the corresponding subgroup of
the Geroch group.Comment: 43 page
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