27,041 research outputs found
Thermodynamic Limit for Mean-Field Spin Models
If the Boltzmann-Gibbs state of a mean-field -particle system
with Hamiltonian verifies the condition for every decomposition , then its free
energy density increases with . We prove such a condition for a wide class
of spin models which includes the Curie-Weiss model, its p-spin generalizations
(for both even and odd p), its random field version and also the finite pattern
Hopfield model. For all these cases the existence of the thermodynamic limit by
subadditivity and boundedness follows.Comment: 15 pages, few improvements. To appear in MPE
Design Of An Induction Probe For Simultaneous Measurements Of Permittivity And Resistivity
In this paper, we propose a discussion of the theoretical design and move
towards the development and engineering of an induction probe for electrical
spectroscopy which performs simultaneous and non invasive measurements on the
electrical RESistivity \rho and dielectric PERmittivity \epsilon r of
non-saturated terrestrial ground and concretes (RESPER probe). In order to
design a RESPER which measures \rho and \epsilon r with inaccuracies below a
prefixed limit (10%) in a band of low frequencies (LF) (B=100kHz), the probe
should be connected to an appropriate analogical digital converter (ADC), which
samples in uniform or in phase and quadrature (IQ) mode, otherwise to a lock-in
amplifier. The paper develops only a suitable number of numerical simulations,
using Mathcad, which provide the working frequencies, the electrode-electrode
distance and the optimization of the height above ground minimizing the
inaccuracies of the RESPER, in galvanic or capacitive contact with terrestrial
soils or concretes, of low or high resistivity. As findings of simulations, we
underline that the performances of a lock-in amplifier are preferable even when
compared to an IQ sampling ADC with high resolution, under the same operating
conditions. As consequences in the practical applications: if the probe is
connected to a data acquisition system (DAS) as an uniform or an IQ sampler,
then it could be commercialized for companies of building and road paving,
being employable for analyzing "in situ" only concretes; otherwise, if the DAS
is a lock-in amplifier, the marketing would be for companies of geophysical
prospecting, involved to analyze "in situ" even terrestrial soils.Comment: 37 pages, 7 figures, 3 table
Pansharpening techniques to detect mass monument damaging in Iraq
The recent mass destructions of monuments in Iraq cannot be monitored with the terrestrial survey methodologies, for obvious reasons
of safety. For the same reasons, it’s not advisable the use of classical aerial photogrammetry, so it was obvious to think to the use of
multispectral Very High Resolution (VHR) satellite imagery. Nowadays VHR satellite images resolutions are very near airborne
photogrammetrical images and usually they are acquired in multispectral mode. The combination of the various bands of the images
is called pan-sharpening and it can be carried on using different algorithms and strategies. The correct pansharpening methodology,
for a specific image, must be chosen considering the specific multispectral characteristics of the satellite used and the particular
application. In this paper a first definition of guidelines for the use of VHR multispectral imagery to detect monument destruction in
unsafe area, is reported.
The proposed methodology, agreed with UNESCO and soon to be used in Libya for the coastal area, has produced a first report
delivered to the Iraqi authorities. Some of the most evident examples are reported to show the possible capabilities of identification of
damages using VHR images
Asymptotics of LQG fusion coefficients
The fusion coefficients from SO(3) to SO(4) play a key role in the definition
of spin foam models for the dynamics in Loop Quantum Gravity. In this paper we
give a simple analytic formula of the EPRL fusion coefficients. We study the
large spin asymptotics and show that they map SO(3) semiclassical intertwiners
into semiclassical intertwiners. This non-trivial
property opens the possibility for an analysis of the semiclassical behavior of
the model.Comment: 14 pages, minor change
On the reconstruction of planar lattice-convex sets from the covariogram
A finite subset of is said to be lattice-convex if is
the intersection of with a convex set. The covariogram of
is the function associating to each u \in
\integer^d the cardinality of . Daurat, G\'erard, and Nivat and
independently Gardner, Gronchi, and Zong raised the problem on the
reconstruction of lattice-convex sets from . We provide a partial
positive answer to this problem by showing that for and under mild extra
assumptions, determines up to translations and reflections. As a
complement to the theorem on reconstruction we also extend the known
counterexamples (i.e., planar lattice-convex sets which are not
reconstructible, up to translations and reflections) to an infinite family of
counterexamples.Comment: accepted in Discrete and Computational Geometr
Variable sequence of events during the past seven terminations in two deep-sea cores from the Southern Ocean
The relationships among internally consistent records of summer sea-surface temperature (SSST), winter sea
ice (WSI), and diatomaceous stable isotopes were studied across seven terminations over the last 660 ka in
sedimentary cores from ODP sites 1093 and 1094. The sequence of events at both sites indicates that SSST
and WSI changes led the carbon and nitrogen isotopic changes in three Terminations (TI, TII and TVI) and followed
them in the other four Terminations (TIII, TIV, TV and TVII). In both TIII and TIV, the leads and lags between
the proxies were related to weak glacial mode, while in TV and TVII they were due to the influence of
the mid-Pleistocene transition. We show that the sequence of events is not unique and does not follow the
same pattern across terminations, implying that the processes that initiated climate change in the Southern
Ocean has varied through time
Real Time 3D Ionospheric Modelling with Ray Tracing Application over Mediterranean Area
This poster deals with some practical examples of instantaneous 3D modelling of regional ionosphere, based on ionosondes data from the Istituto Nazionale di Geofisica
e Vulcanologia, INGV.
Characteristic anchor points have been chosen for each ionospheric region. These points are joint by an adaptive ionospheric profiler derived from the one used in
Autoscala. For the F2 region the anchor point is given by the real height hmF2 of the layer and its critical frequency foF2. These values are obtained basing on the
observed heights (hmF2ROME[OBS] and hmF2GIBILMANNA[OBS]) and critical frequencies (foF2ROME[OBS] and foF2GIBILMANNA[OBS]) of the F2 layer, which are compared with the corresponding monthly median given by CCIR maps using Shimazaki’s formulation.
The differences
dhmF2ROME = hmF2ROME[OBS] - hmF2ROME[CCIR]
dhmF2GIBILMANNA = hmF2 GIBILMANNA [OBS] - hmF2 GIBILMANNA [CCIR]
are thus computed and used in Kriging method to update the values given by CCIR maps.
For the F1 region the critical frequency is derived form a solar zenith angle dependent model adjusted to match the values of foF1 measured in Rome and Gibilmanna.
For the E region the height is set to 110 km, while the critical frequency is estimated by a standard solar zenith angle and solar activity dependent model.
The model produces as an output a 3D matrix which can be profitably used as an input for a Matlab/Fortran based ray tracing program recently developed at INGV
Simple model for quantum general relativity from loop quantum gravity
New progress in loop gravity has lead to a simple model of `general-covariant
quantum field theory'. I sum up the definition of the model in self-contained
form, in terms accessible to those outside the subfield. I emphasize its
formulation as a generalized topological quantum field theory with an infinite
number of degrees of freedom, and its relation to lattice theory. I list the
indications supporting the conjecture that the model is related to general
relativity and UV finite.Comment: 8 pages, 3 figure
The EPRL intertwiners and corrected partition function
Do the SU(2) intertwiners parametrize the space of the EPRL solutions to the
simplicity constraint? What is a complete form of the partition function
written in terms of this parametrization? We prove that the EPRL map is
injective for n-valent vertex in case when it is a map from SO(3) into
SO(3)xSO(3) representations. We find, however, that the EPRL map is not
isometric. In the consequence, in order to be written in a SU(2) amplitude
form, the formula for the partition function has to be rederived. We do it and
obtain a new, complete formula for the partition function. The result goes
beyond the SU(2) spin-foam models framework.Comment: RevTex4, 15 pages, 5 figures; theorem of injectivity of EPRL map
correcte
- …