Particle Currents in a Space-Time dependent and CP-violating Higgs Background: a Field Theory Approach

Motivated by cosmological applications like electroweak baryogenesis, we develop a field theoretic approach to the computation of particle currents on a space-time dependent and CP-violating Higgs background. We consider the Standard Model model with two Higgs doublets and CP violation in the scalar sector, and compute both fermionic and Higgs currents by means of an expansion in the background fields. We discuss the gauge dependence of the results and the renormalization of the current operators, showing that in the limit of local equilibrium, no extra renormalization conditions are needed in order to specify the system completely.Comment: 21 pages, LaTeX file, uses epsf.sty. 4 figures available as a compressed .ep

Stars and (Furry) Black Holes in Lorentz Breaking Massive Gravity

We study the exact spherically symmetric solutions in a class of Lorentz-breaking massive gravity theories, using the effective-theory approach where the graviton mass is generated by the interaction with a suitable set of Stuckelberg fields. We find explicitly the exact black hole solutions which generalizes the familiar Schwarzschild one, which shows a non-analytic hair in the form of a power-like term r^\gamma. For realistic self-gravitating bodies, we find interesting features, linked to the effective violation of the Gauss law: i) the total gravitational mass appearing in the standard 1/r term gets a multiplicative renormalization proportional to the area of the body itself; ii) the magnitude of the power-like hairy correction is also linked to size of the body. The novel features can be ascribed to presence of the goldstones fluid turned on by matter inside the body; its equation of state approaching that of dark energy near the center. The goldstones fluid also changes the matter equilibrium pressure, leading to an upper limit for the graviton mass, m <~ 10^-28 - 10^29 eV, derived from the largest stable gravitational bound states in the Universe.Comment: 22 pages, 4 Figures. Final version to be published in PRD. Typos corrected, comments adde

Spontaneous Lorentz Breaking and Massive Gravity

We study a theory where the presence of an extra spin-two field coupled to gravity gives rise to a phase with spontaneously broken Lorentz symmetry. In this phase gravity is massive, and the Weak Equivalence Principle is respected. The newtonian potentials are in general modified, but we identify an non-perturbative symmetry that protects them. The gravitational waves sector has a rich phenomenology: sources emit a combination of massless and massive gravitons that propagate with distinct velocities and also oscillate. Since their velocities differ from the speed of light, the time of flight difference between gravitons and photons from a common source could be measured.Comment: 4 page

DOMANDE E RISPOSTE SUL SISTEMA INTEGRATO DI VALUTAZIONE PREVENTIVA DELL'INQUINAMENTO ELETTROMAGNETICO AMBIENTALE A BASSISSIMA FREQUENZA PLEIA-CERT

L’ARPAT e l’IFAC-CNR collaborano ormai da oltre cinque anni allo sviluppo del Catasto degli Elettrodotti della Regione Toscana (CERT) e di un sistema integrato di applicazioni, denominato PLEIA (Power Line Electromagnetic Impact Assessment), per il suo utilizzo ai fini del calcolo del campo magnetico nello spazio circostante gli elettrodotti e, in particolare, della determinazione delle fasce di rispetto. Per rendere possibile a queste istituzioni un utilizzo corretto e consapevole degli strumenti realizzati e dei risultati da essi forniti, è stato indispensabile documentare innanzitutto i presupposti tecnici e metodologici che stanno alla base delle applicazioni sviluppate: a questo scopo, è venuto spontaneamente a crearsi un gruppo di lavoro informale tra esperti dell’ARPAT, dell’IFAC e della Regione Toscana. Il gruppo ha lavorato secondo un meccanismo virtuoso in cui, da un lato, si è cercato di formulare quesiti puntuali e ben definiti e, dall'altro, di rispondervi nel modo più chiaro ed esauriente possibile. Ne è scaturito un documento a domande e risposte che, opportunamente modificato, è riproposto in questa sede, perché mette in evidenza in modo semplice ma non banale alcuni rilevanti aspetti tecnici, e costituisce un buon documento introduttivo sulle potenzialità del sistema sviluppato. Le prime domande riguardano il sistema PLEIA-CERT in generale, mentre nella seconda parte si approfondiscono in particolare le modalità di calcolo delle fasce di rispetto che, anche alla luce di recenti sviluppi normativi, hanno assunto un ruolo di primaria importanza

Il sistema integrato di valutazione preventiva dell?inquinamento elettromagnetico ambientale a bassissima frequenza PLEIA?CERT

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Neutral Heavy Leptons and Electroweak Baryogenesis

We investigate the possibility that baryogenesis occurs during the weak phase transition in a minimal extension of the Standard Model which contains extra neutral leptons and conserves total lepton number. The necessary CP-violating phases appear in the leptonic Yukawa couplings. We compute the CP-asymmetries in both the neutral and the charged lepton fluxes reflected on the bubble wall. Using present experimental bounds on the mixing angles and Standard Model estimates for the parameters related to the scalar potential, we conclude that it seems unlikely to produce the observed baryon to entropy ratio within this type of models. We comment on the possibility that the constraints on the mixings might be naturally relaxed due to small finite temperature effects.Comment: 21 pages (4 Figures

Field Evolution leading to hybrid inflation

In general the onset of hybrid inflation requires an extremely homogeneous field configuration at the end of Planck era. The field \phi orthogonal to the inflaton \sigma must be zero with high accuracy over the range exceeding the initial horizon size \sim m_{Pl}^{-1} by about two orders of magnitude. We consider a supersymmetric model that permits the decay of the oscillating field \phi into light particles. We study the field evolution and find that the requirement of the extreme homogeneity can be relaxed. However, the field \phi must still be smaller than the inflaton by a factor of order 1 over a region far exceeding the initial horizon size.Comment: Latex, 9 pages, 3 figure

Deep learning-based methods for prostate segmentation in magnetic resonance imaging

Magnetic Resonance Imaging-based prostate segmentation is an essential task for adaptive radiotherapy and for radiomics studies whose purpose is to identify associations between imaging features and patient outcomes. Because manual delineation is a time-consuming task, we present three deep-learning (DL) approaches, namely UNet, efficient neural network (ENet), and efficient residual factorized convNet (ERFNet), whose aim is to tackle the fully-automated, real-time, and 3D delineation process of the prostate gland on T2-weighted MRI. While UNet is used in many biomedical image delineation applications, ENet and ERFNet are mainly applied in self-driving cars to compensate for limited hardware availability while still achieving accurate segmentation. We apply these models to a limited set of 85 manual prostate segmentations using the k-fold validation strategy and the Tversky loss function and we compare their results. We find that ENet and UNet are more accurate than ERFNet, with ENet much faster than UNet. Specifically, ENet obtains a dice similarity coefficient of 90.89% and a segmentation time of about 6 s using central processing unit (CPU) hardware to simulate real clinical conditions where graphics processing unit (GPU) is not always available. In conclusion, ENet could be efficiently applied for prostate delineation even in small image training datasets with potential benefit for patient management personalization

Towards Collinear Evolution Equations in Electroweak Theory

We consider electroweak radiative corrections to hard inclusive processes at the TeV scale, and we investigate how collinear logarithms factorize in a spontaneously broken gauge theory, similarly to the DGLAP analysis in QCD. Due to the uncancelled double logs noticed previously, we find a factorization pattern which is qualitatively different from the analogous one in QCD. New types of splitting functions emerge which are needed to describe the initial beam charges and are infrared-sensitive, that is dependent on an infrared cutoff provided, ultimately, by the symmetry breaking scale. We derive such splitting functions at one-loop level in the example of SU(2) gauge theory, and we also discuss the structure functions' evolution equations, under the assumption that isospin breaking terms present in the Ward identities of the theory are sufficiently subleading at higher orders.Comment: 5 pages, 3 figure

On the Spontaneous CP Breaking at Finite Temperature in a Nonminimal Supersymmetric Standard Model

We study the spontaneous CP breaking at finite temperature in the Higgs sector in the Minimal Supersymmetric Standard Model with a gauge singlet. We consider the contribution of the standard model particles and that of stops, charginos, neutralinos, charged and neutral Higgs boson to the one-loop effective potential. Plasma effects for all bosons are also included. Assuming CP conservation at zero temperature, so that experimental constraints coming from, {\it e.g.}, the electric dipole moment of the neutron are avoided, and the electroweak phase transition to be of the first order and proceeding via bubble nucleation, we show that spontaneous CP breaking cannot occur inside the bubble mainly due to large effects coming from the Higgs sector. However, spontaneous CP breaking can be present in the region of interest for the generation of the baryon asymmetry, namely inside the bubble wall. The important presence of very tiny explicit CP violating phases is also commented.Comment: 28 pages, 4 figures available upon request, DFPD 94/TH/38 and SISSA 94/81-A preprint