Search results for "Phase Transition"
showing 10 items of 1281 documents
Bounds on Neutrino Transition Magnetic Moments in Random Magnetic Fields
1995
We consider the conversions of active to sterile Majorana neutrinos $\nu_{a}$ and $\nu_{s}$, due to neutrino transition magnetic moments in the presence of random magnetic fields (r.m.f.) generated at the electroweak phase transition. From a simple Schr\"{o}dinger-type evolution equation, we derive a stringent constraint on the corresponding transition magnetic moments and display it as a function of the domain size and field geometry. For typical parameter choices one gets limits much stronger than usually derived from stellar energy loss considerations. These bounds are consistent with the hypothesis of seeding of galactic magnetic fields by primordial fields surviving past the re-combina…
A Unified Approach to High Density: Pion Fluctuations in Skyrmion Matter
2003
As the first in a series of systematic work on dense hadronic matter, we study the properties of the pion in dense medium using Skyrme's effective Lagrangian as a unified theory of the hadronic interactions applicable in the large $N_c$ limit. Dense baryonic matter is described as the ground state of a skyrmion matter which appears in two differentiated phases as a function of matter density: i) at high densities as a stable cubic-centered (CC) half-skyrmion crystal; ii) at low densities as an unstable face-centered cubic (FCC) skyrmion crystal. We substitute the latter by a stable inhomogeneous phase of lumps of dense matter, which represents a naive Maxwell construction of the phase trans…
The Pion Velocity in Dense Skyrmion Matter
2003
We have developed a field theory formalism to calculate $in$-$medium$ properties of hadrons within a unified approach that exploits a single Lagrangian to describe simultaneously both matter background and meson fluctuations. In this paper we discuss the consequences on physical observables of a possible phase transition of hadronic matter taking place in the chiral limit. We pay special attention to the pion velocity $v_\pi$, which controls, through a dispersion relation, the pion propagation in the hadronic medium. The $v_\pi$ is defined in terms of parameters related to the matrix element in matter of the axial-vector current, namely, the in-medium pion decay constants, $f_t$ and $f_s$. …
Hydrodynamical Description of 200 A GeV/c S+Au Collisions: Hadron and Electromagnetic Spectra
1996
We study relativistic S+Au collisions at 200 A GeV/c using a hydrodynamical approach. We test various equations of state (EOSs), which are used to describe the strongly interacting matter at densities attainable in the CERN-SPS heavy ion experiments. For each EOS, suitable initial conditions can be determined to reproduce the experimental hadron spectra; this emphasizes the ambiguity between the initial conditions and the EOS in such an approach. Simultaneously, we calculate the resulting thermal photon and dielectron spectra, and compare with experiments. If one allows the excitation of resonance states with increasing temperature, the electro-magnetic signals from scenarios with and witho…
Electroweak phase transition in left-right symmetric models
1998
We study the finite-temperature effective potential of minimal left-right symmetric models containing a bidoublet and two triplets in the scalar sector. We perform a numerical analysis of the parameter space compatible with the requirement that baryon asymmetry is not washed out by sphaleron processes after the electroweak phase transition. We find that the spectrum of scalar particles for these acceptable cases is consistent with present experimental bounds.
Three-Dimensional 3-State Potts Model Revisited With New Techniques
1997
We report a fairly detailed finite-size scaling analysis of the first-order phase transition in the three-dimensional 3-state Potts model on cubic lattices with emphasis on recently introduced quantities whose infinite-volume extrapolations are governed `only' by exponentially small terms. In these quantities no asymptotic power series in the inverse volume are involved which complicate the finite-size scaling behaviour of standard observables related to the specific-heat maxima or Binder-parameter minima. Introduced initially for strong first-order phase transitions in q-state Potts models with ``large enough'' q, the new techniques prove to be surprisingly accurate for a q value as small …
Sensitivity of jet quenching to enhancement of the medium opacity near TC
2014
One of the main goals of the study of high transverse momentum (P_T) observables in the context of ultrarelativisic heavy-ion collisions is the determination of properties of the produced QCD matter. In particular, the transport coefficients qhat and ehat, characterizing the interaction of the medium with a high p_T parton, are accessible via high P_T probes. However, a precision extraction of their temperature dependence from current data faces the problem that neither the spacetime geometry of the evolving matter droplet nor the link between thermodynamics and transport coefficients is unambiguously known, and various conjectured scenarios how thermodynamics and transport coefficients beh…
IBFFM predictions for low-lying spherical states in the shape-coexisting odd-odd nucleus98Y
1989
Extrapolating the Interacting Boson-Model treatment from lighter neighbours to98Y we predict the properties of low-lying states of spherical nature in IBFFM. This odd-odd nucleus which presents one of the rare cases of coexisting spherical and deformed shapes is of fundamental importance for understanding nuclear phase transitions.
Skyrmions at finite density and temperature: the chiral phase transition
2008
The Skyrme model, an effective low energy theory rooted in large $N_c$ QCD, has been applied to the study of dense matter. Matter is described by various crystal structures of skyrmions. When this system is heated, the dominating thermal degrees of freedom are the fluctuating pions. Taking these mechanisms jointly produces a description of the chiral phase transition leading to the conventional phase diagram with critical temperatures and densities in agreement with expected values.
Theories relating baryon asymmetry and dark matter
2014
The nature of dark matter and the origin of the baryon asymmetry are two of the deepest mysteries of modern particle physics. In the absence of hints regarding a possible solution to these mysteries, many approaches have been developed to tackle them simultaneously leading to very diverse and rich models. We give a short review where we describe the general features of some of these models and an overview on the general problem. We also propose a diagrammatic notation to label the different models.