5,417 research outputs found
The elliptic scattering theory of the 1/2-XYZ and higher order Deformed Virasoro Algebras
Bound state excitations of the spin 1/2-XYZ model are considered inside the
Bethe Ansatz framework by exploiting the equivalent Non-Linear Integral
Equations. Of course, these bound states go to the sine-Gordon breathers in the
suitable limit and therefore the scattering factors between them are explicitly
computed by inspecting the corresponding Non-Linear Integral Equations. As a
consequence, abstracting from the physical model the Zamolodchikov-Faddeev
algebra of two -th elliptic breathers defines a tower of -order Deformed
Virasoro Algebras, reproducing the case the usual well-known algebra of
Shiraishi-Kubo-Awata-Odake \cite{SKAO}.Comment: Latex version, 13 page
Beyond cusp anomalous dimension from integrability in SYM
We study the first sub-leading correction to the cusp
anomalous dimension in the high spin expansion of finite twist operators in
SYM theory. This term is still governed by a linear integral
equation which we study in the weak and strong coupling regimes. In the strong
coupling regime we find agreement with the string theory computationsComment: 5 pages, contribution to the proceedings of the workshop Diffraction
2010, Otranto, 10th-15th September, talk given by M.Rossi; v2: references
adde
Asymptotic Bethe Ansatz on the GKP vacuum as a defect spin chain: scattering, particles and minimal area Wilson loops
Moving from Beisert-Staudacher equations, the complete set of Asymptotic
Bethe Ansatz equations and -matrix for the excitations over the GKP vacuum
is found. The resulting model on this new vacuum is an integrable spin chain of
length ( spin) with particle rapidities as inhomogeneities, two
(purely transmitting) defects and (residual R-)symmetry. The
non-trivial dynamics of SYM appears in elaborated dressing factors
of the 2D two-particle scattering factors, all depending on the 'fundamental'
one between two scalar excitations. From scattering factors we determine bound
states. In particular, we study the strong coupling limit, in the
non-perturbative, perturbative and giant hole regimes. Eventually, from these
scattering data we construct the pentagon transition amplitudes
(perturbative regime). In this manner, we detail the multi-particle
contributions (flux tube) to the MHV gluon scattering amplitudes/Wilson loops
(OPE or BSV series) and re-sum them to the Thermodynamic Bubble Ansatz.Comment: 103 pages; typos corrected, references added: journal versio
Rate-Distortion Classification for Self-Tuning IoT Networks
Many future wireless sensor networks and the Internet of Things are expected
to follow a software defined paradigm, where protocol parameters and behaviors
will be dynamically tuned as a function of the signal statistics. New protocols
will be then injected as a software as certain events occur. For instance, new
data compressors could be (re)programmed on-the-fly as the monitored signal
type or its statistical properties change. We consider a lossy compression
scenario, where the application tolerates some distortion of the gathered
signal in return for improved energy efficiency. To reap the full benefits of
this paradigm, we discuss an automatic sensor profiling approach where the
signal class, and in particular the corresponding rate-distortion curve, is
automatically assessed using machine learning tools (namely, support vector
machines and neural networks). We show that this curve can be reliably
estimated on-the-fly through the computation of a small number (from ten to
twenty) of statistical features on time windows of a few hundreds samples
On the scattering over the GKP vacuum
By converting the Asymptotic Bethe Ansatz (ABA) of SYM into
non-linear integral equations, we find 2D scattering amplitudes of excitations
on top of the GKP vacuum. We prove that this is a suitable and powerful set-up
for the understanding and computation of the whole S-matrix. We show that all
the amplitudes depend on the fundamental scalar-scalar one.Comment: final version, 14 pages, to appear in Physics Letters
Quantum Monte Carlo study of a vortex in superfluid He and search for a vortex state in the solid
We have performed a microscopic study of a straight quantized vortex line in
three dimensions in condensed He at zero temperature using the Shadow Path
Integral Ground State method and the fixed-phase approximation. We have
characterized the energy and the local density profile around the vortex axis
in superfluid He at several densities, ranging from below the equilibrium
density up to the overpressurized regime. For the Onsager-Feynman (OF) phase
our results are exact and represent a benchmark for other theories. The
inclusion of backflow correlations in the phase improves the description of the
vortex with respect to the OF phase by a large reduction of the core energy of
the topological excitation. At all densities the phase with backflow induces a
partial filling of the vortex core and this filling slightly increases with
density. The core size slightly decreases for increasing density and the
density profile has well defined density dependent oscillations whose wave
vector is closer to the wave vector of the main peak in the static density
response function rather than to the roton wave vector. Our results can be
applied to vortex rings of large radius and we find good agreement with the
experimental value of the energy as function of without any free parameter.
We have studied also He above the melting density in the solid phase using
the same functional form for the phase as in the liquid. We found that
off-diagonal properties of the solid are not qualitatively affected by the
velocity field induced by the vortex phase, both with and without backflow
correlations. Therefore we find evidence that a perfect He crystal is not a
marginally stable quantum solid in which rotation would be able to induce
off-diagonal long-range coherence.Comment: 15 pages, 8 figure
SolarStat: Modeling Photovoltaic Sources through Stochastic Markov Processes
In this paper, we present a methodology and a tool to derive simple but yet
accurate stochastic Markov processes for the description of the energy
scavenged by outdoor solar sources. In particular, we target photovoltaic
panels with small form factors, as those exploited by embedded communication
devices such as wireless sensor nodes or, concerning modern cellular system
technology, by small-cells. Our models are especially useful for the
theoretical investigation and the simulation of energetically self-sufficient
communication systems including these devices. The Markov models that we derive
in this paper are obtained from extensive solar radiation databases, that are
widely available online. Basically, from hourly radiance patterns, we derive
the corresponding amount of energy (current and voltage) that is accumulated
over time, and we finally use it to represent the scavenged energy in terms of
its relevant statistics. Toward this end, two clustering approaches for the raw
radiance data are described and the resulting Markov models are compared
against the empirical distributions. Our results indicate that Markov models
with just two states provide a rough characterization of the real data traces.
While these could be sufficiently accurate for certain applications, slightly
increasing the number of states to, e.g., eight, allows the representation of
the real energy inflow process with an excellent level of accuracy in terms of
first and second order statistics. Our tool has been developed using Matlab(TM)
and is available under the GPL license at[1].Comment: Submitted to IEEE EnergyCon 201
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