3,870 research outputs found
Electroweak Physics at Very High Energy
Aim of the thesis is to review the main quantum field theory tools that are needed to deal with electroweak interactions in the very high energy regime, far above the electroweak scale, and to apply them to a concrete calculation. These tools include the equivalence theorem and the resummation of infrared enhanced effects like the electroweak Sudakov double logarithms. The latter ones are particularly relevant in the case of electroweak interactions because they persist also in inclusive observables, producing sizeable and peculiar effects that change the nature of electroweak physics in very high energy reactions. These effects might be relevant also at the LHC, and they will become essential at future high energy colliders. Concrete applications studied in the thesis will be the prediction of cross-sections at lepton colliders with tenths of TeV center of mass energy, including the production of hypothetical heavy particles via vector boson fusion.ope
Generalized off-equilibrium fluctuation-dissipation relations in random Ising systems
We show that the numerical method based on the off-equilibrium
fluctuation-dissipation relation does work and is very useful and powerful in
the study of disordered systems which show a very slow dynamics. We have
verified that it gives the right information in the known cases (diluted
ferromagnets and random field Ising model far from the critical point) and we
used it to obtain more convincing results on the frozen phase of
finite-dimensional spin glasses. Moreover we used it to study the Griffiths
phase of the diluted and the random field Ising models.Comment: 20 pages, 10 figures, uses epsfig.sty. Partially presented at
StatPhys XX in a talk by one of the authors (FRT). Added 1 reference in the
new versio
Universality in the off-equilibrium critical dynamics of the diluted Ising model
We study the off-equilibrium critical dynamics of the three dimensional
diluted Ising model. We compute the dynamical critical exponent and we show
that it is independent of the dilution only when we take into account the
scaling-corrections to the dynamics. Finally we will compare our results with
the experimental data.Comment: Final Version, 5 Latex pages (RevTeX) plus 3 eps figure
Diluted one-dimensional spin glasses with power law decaying interactions
We introduce a diluted version of the one dimensional spin-glass model with
interactions decaying in probability as an inverse power of the distance. In
this model varying the power corresponds to change the dimension in short-range
models. The spin-glass phase is studied in and out of the range of validity of
the mean-field approximation in order to discriminate between different
theories. Since each variable interacts only with a finite number of others the
cost for simulating the model is drastically reduced with respect to the fully
connected version and larger sizes can be studied. We find both static and
dynamic evidence in favor of the so-called replica symmetry breaking theory.Comment: 4 pages, 6 figures, 2 table
Off-Equilibrium Dynamics at Very Low Temperatures in 3d Spin Glasses
We present a high statistic systematic study of the overlap correlation
function well below the critical temperature in the three dimensional Gaussian
spin glass. The off-equilibrium correlation function has been studied
confirming the power law behavior for the dynamical correlation length. In
particular we have computed the dynamical critical exponent in a wide range
of temperatures, , obtaining a dependence in a
very good agreement with recent experiments. Moreover, we report a study of the
violation of the fluctuation-dissipation theorem for very low temperatures
and . All our numerical results avoid a droplet model
interpretation even when is as low as .Comment: LaTeX, 14 pages and 5 figures. A minor arithmetic error corrected and
references update
Ising spin glass transition in magnetic field out of mean-field
The spin-glass transition in external magnetic field is studied both in and
out of the limit of validity of mean-field theory on a diluted one dimensional
chain of Ising spins where exchange bonds occur with a probability decaying as
the inverse power of the distance. Varying the power in this long-range model
corresponds, in a one-to-one relationship, to change the dimension in
spin-glass short-range models. Evidence for a spin-glass transition in magnetic
field is found also for systems whose equivalent dimension is below the upper
critical dimension at zero magnetic field.Comment: 5 pages, 1 table, 6 figures, data analysis mistake corrected, new
figures, new scaling approach to critical properties introduce
Replica Symmetry Breaking in Short-Range Spin Glasses: Theoretical Foundations and Numerical Evidences
We discuss replica symmetry breaking (RSB) in spin glasses. We update work in
this area, from both the analytical and numerical points of view. We give
particular attention to the difficulties stressed by Newman and Stein
concerning the problem of constructing pure states in spin glass systems. We
mainly discuss what happens in finite-dimensional, realistic spin glasses.
Together with a detailed review of some of the most important features, facts,
data, and phenomena, we present some new theoretical ideas and numerical
results. We discuss among others the basic idea of the RSB theory, correlation
functions, interfaces, overlaps, pure states, random field, and the dynamical
approach. We present new numerical results for the behaviors of coupled
replicas and about the numerical verification of sum rules, and we review some
of the available numerical results that we consider of larger importance (for
example, the determination of the phase transition point, the correlation
functions, the window overlaps, and the dynamical behavior of the system).Comment: 48 pages, 21 figures. v2: the published versio
AutoDIAL: Automatic DomaIn Alignment Layers
Classifiers trained on given databases perform poorly when tested on data
acquired in different settings. This is explained in domain adaptation through
a shift among distributions of the source and target domains. Attempts to align
them have traditionally resulted in works reducing the domain shift by
introducing appropriate loss terms, measuring the discrepancies between source
and target distributions, in the objective function. Here we take a different
route, proposing to align the learned representations by embedding in any given
network specific Domain Alignment Layers, designed to match the source and
target feature distributions to a reference one. Opposite to previous works
which define a priori in which layers adaptation should be performed, our
method is able to automatically learn the degree of feature alignment required
at different levels of the deep network. Thorough experiments on different
public benchmarks, in the unsupervised setting, confirm the power of our
approach.Comment: arXiv admin note: substantial text overlap with arXiv:1702.06332
added supplementary materia
Bond diluted Levy spin-glass model and a new finite size scaling method to determine a phase transition
A spin-glass transition occurs both in and out of the limit of validity of
mean-field theory on a diluted one dimensional chain of Ising spins where
exchange bonds occur with a probability decaying as the inverse power of the
distance. Varying the power in this long-range model corresponds, in a
one-to-one relationship, to change the dimension in spin-glass short-range
models. Using different finite size scaling methods evidence for a spin-glass
transition is found also for systems whose equivalent dimension is below the
upper critical dimension at zero magnetic field. The application of a new
method is discussed, that can be exported to systems in a magnetic field.Comment: 8 pages, 8 figures, 1 tabl
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