Symmetry structure and phase transitions (original) (raw)

Non-Equilibrium Dynamics of Phase Transitions: From the Early Universe to Chiral Condensates

1994

In this brief review we introduce the methods of quantum field theory out of equilibrium and study the non-equilibrium aspects of phase transitions. Specifically we critically study the picture of the ``slow-roll'' phase transition in the new inflationary models, we show that the instabilities that are the hallmark of the phase transition, that is the formation of correlated domains, dramatically change this picture. We analyze in detail the dynamics of phase separation in strongly supercooled phase transitions in Minkowski space. We argue that this is typically the situation in weakly coupled scalar theories. The effective evolution equations for the expectation value and the fluctuations of an inflaton field in a FRW cosmology are derived both in the loop expansion and in a self-consistent non-perturbative scheme. Finally we use these non-equilibrium techniques and concepts to study the influence of quantum and thermal fluctuations on the dynamics of a proposed mechanism for the formation of disoriented chiral condensates during a rapid phase transition out of equilibrium. This last topic may prove to be experimentally relevant at present accelerator energies. To appear in the Proceedings of the `2nd. Journ\'ee Cosmologie', Observatoire de Paris, 2-4, June 1994. H J de Vega and N. S\'anchez, Editors, World Scientific.

Symmetries,Dynamical Evolution of Phase Transition and Nugget Formation

We study the influence of the presence of a magnetic field on chiral symmetry in the core of compact stars and in the early Universe. We find that the effect of a magnetic field is to enhance the chiral symmetry breaking in the sense that, in the presence of magnetic field, chiral symmetry gets restored at a higher temperature and density compared to the case where there is no magnetic field. However, the effect of a super strong magnetic field is to restore again chiral symmetry. We then investigate the dynamical evolution of the confinement-deconfinement phase transition in the expanding early Universe through bubble nucleation, taking into account reheating due to the heat released during the expansion of hadronic bubbles. We estimate the degree of supercooling and the time required to complete the phase transition. We then consider the formation of quark nuggets and their possible survival against boiling and evaporation to the present epoch.

Vacuum structure and chiral symmetry breaking in strong magnetic fields for hot and dense quark matter

Physical Review D, 2011

We investigate chiral symmetry breaking in strong magnetic fields at finite temperature and densities in a 3 flavor Nambu Jona Lasinio (NJL) model including the Kobayashi Maskawa t-Hooft (KMT) determinant term, using an explicit structure for the ground state in terms of quark antiquark condensates. The mass gap equations are solved self consistently and are used to compute the thermodynamic potential. We also derive the equation of state for strange quark matter in the presence of strong magnetic fields which could be relevant for proto-neutron stars.

Crystalline chiral condensates as a component of compact stars

Physical Review D, 2015

We investigate the influence of spatially inhomogeneous chiral symmetry-breaking condensates in a magnetic field background on the equation of state for compact stellar objects. After building a hybrid star composed of nuclear and quark matter using the Maxwell construction, we find, by solving the Tolman-Oppenheimer-Volkoff equations for stellar equilibrium, that our equation of state supports stars with masses around 2 M for values of the magnetic field that are in accordance with those inferred from magnetar data. The inclusion of a weak vector interaction term in the quark part allows to reach 2 solar masses for relatively small central magnetic fields, making this composition a viable possibility for describing the internal degrees of freedom of this class of astrophysical objects.

Self-Consistent Evolution of Magnetic Fields and Chiral Asymmetry in the Early Universe

Physical Review Letters, 2012

We show that the evolution of magnetic fields in a primordial plasma, filled with Standard Model particles, at temperatures T 10MeV is strongly affected by the quantum chiral anomaly -an effect that has been neglected previously. Although reactions equilibrating left and right-chiral electrons are in deep thermal equilibrium for T 80 TeV, an asymmetry between these particle develops in the presence of strong magnetic fields. This results in magnetic helicity transfer from shorter to longer scales. This also leads to an effective generation of lepton asymmetry that may survive in the plasma down to temperatures T ∼ 10 MeV, which may strongly affect many processes in the early Universe. Although we report our results for the Standard Model, they are likely to play an important role also in its extensions.

Quark-hadron phase transitions in the viscous early universe

Physical Review D, 2012

In the standard hot big bang theory, when the Universe was about 1-10 s old, the cosmological matter is conjectured to undergo quantum chromodynamics (QCD) phase transition(s) from quark matter to hadrons. In the present work, we study the cosmological quark-hadron phase transition in two different physical scenarios. First, by assuming that the phase transition would be described by an effective nucleation theory (prompt first-order phase transition), we analyze the evolution of the relevant cosmological parameters of the early universe (energy density , temperature T, Hubble parameter H, and the scale factor a) before, during, and after the phase transition. To study the cosmological dynamics and the time evolution, we use both analytical and numerical methods. The case where the Universe evolved through a mixed phase with a small initial supercooling and monotonically growing hadronic bubbles is also considered in detail. The numerical estimation of the cosmological parameters, a and H for instance, shows that the time evolution of the Universe varies from phase to phase. As the QCD era turns to be fairly accessible in the high-energy experiments and the lattice QCD simulations, the QCD equation of state is very well defined. In light of these QCD results, we develop a systematic study of the crossover quark-hadron phase transition, and an estimation for the time evolution of the Hubble parameter during the crossover.

Quantum chromodynamics phase transition in the early Universe and quark nuggets

Pramana, 2003

A first-order quark hadron phase transition in the early Universe may lead to the formation of quark nuggets. The baryon number distribution of these quark nuggets have been calculated and it has been found that there are sizeable number of quark nuggets in the stable sector. The nuggets can clump and form bigger objects in the mass range of 0 0003M ¬ to 0 12M ¬. It has been discussed that these bigger objects can be possible candidates for cold dark matter.

On the role of the strange quark and its mass in the chiral phase transition

2002

The evolution of the chiral condensate with the temperature is studied using SU(3) Chiral Perturbation Theory and the virial expansion. We observe a large decrease of the melting temperature of the non-strange condensate compared with the SU(2) case. Due to the larger mass of the strange quark we also find an slower temperature evolution of the strange condensate compared with the non-strange condensate.

Quark-Hadron Phase Transitions in Viscous Early Universe

Arxiv preprint arXiv:1108.5697, 2011

The quark-hadron transition in the early universe

Nuclear Physics A, 1991

The application of quantum chromcdynamics to big bang cosmology predicts that the universe underwent a transition from a quark-gluon plasma to a confined hadronic phase when it was roughly lo-' seconds old. A first order phase transition in QCD can produce baryon density inhomogeneities in an initially homogeneous universe. Neutron diffusion converts these density inhomogeneities into variations in the local ratio of neutrons to protons, and these variations can produce detectable features in the pattern of abundances produced in primordial nucleoeynthesis. In addition, the deviation from equilibrium needed to drive the phase transition can result in the production of primordial magnetic fields.

Metastable strange matter and compact quark stars

Journal of Physics G: Nuclear and Particle Physics, 2003

Strange quark matter in beta equilibrium at high densities is studied in a quark confinement model. Two equations of state are dynamically generated for the same set of model parameters used to describe the nucleon: one corresponds to a chiral restored phase with almost massless quarks and the other to a chiral broken phase. The chiral symmetric phase saturates at around five times the nuclear matter density. Using the equation of state for this phase, compact bare quark stars are obtained with radii and masses in the ranges R ∼ 5 − 8 km and M ∼ M ⊙. The energy per baryon number decreases very slowly from the center of the star to the periphery, remaining above the corresponding values for the iron or the nuclear matter, even at the edge. Our results point out that strange quark matter at very high densities may not be absolutely stable and the existence of an energy barrier between the two phases may prevent the compact quarks stars to decay to hybrid stars.

Phase Transitions in the Universe 1

1998

During the past two decades, cosmologists turned to particle physics in order to explore the physics of the very early Universe. The main link between the physics of the smallest and largest structures in the Universe is the idea of spontaneous symmetry breaking, familiar from condensed matter physics. Implementing this mechanism into cosmology leads to the interesting possibility that phase transitions related to the breaking of symmetries in high energy particle physics took place during the early history of the Universe. These cosmological phase transitions may help us 1 Invited article for Contemporary Physics. NSF Presidential Faculty Fellow. email: gleiser@dartmouth.edu Permanent address.

Dynamical evolution of the Universe in the quark-hadron phase transition and nugget formation

Physical Review D, 2000

We study the dynamics of first-order phase transition in the early Universe when it was 10-50µs old with quarks and gluons condensing into hadrons. We look at how the Universe evolved through the phase transition in small as well as large super cooling scenario, specifically exploring the formation of quark nuggets and their possible survival. The nucleation of the hadron phase introduces new distance scales in the Universe, which we estimate along with the hadron fraction, temperature, nucleation time etc. It is of interest to explore whether there is a relic signature of this transition in the form of quark nuggets which might be identified with the recently observed dark objects in our galactic halo and account for the Dark Matter

Chirality in the Early Universe

arXiv: High Energy Physics - Phenomenology, 1995

The early big bang is an alphabet soup of quarks, W bosons, gluons, and other exotic particles and flavors. In the usual scenario, there is no place for the pion. It dissociates in the alphabet soup of the early universe. I will show that this scenario is naive. The thermal vacuum is a far more complex state, and the pion remains a Nambu-Goldstone particle at high TTT, and will not dissociate. It propagates at the speed of light but {\\em with a halo}.

Time evolution of the chiral phase transition during a spherical expansion

Physical Review D, 1996

We examine the non-equilibrium time evolution of the hadronic plasma produced in a relativistic heavy ion collision, assuming a spherical expansion into the vacuum. We study the O(4) linear sigma model to leading order in a large-N expansion. Starting at a temperature above the phase transition, the system expands and cools, finally settling into the broken symmetry vacuum state. We consider the proper time evolution of the effective pion mass, the order parameter σ , and the particle number distribution. We examine several different initial conditions and look for instabilities (exponentially growing long wavelength modes) which can lead to the formation of disoriented chiral condensates (DCCs). We find that instabilities exist for proper times which are less than 3 fm/c. We also show that an experimental signature of domain growth is an increase in the low momentum spectrum of outgoing pions when compared to an expansion in thermal equilibrium. In comparison to particle production during a longitudinal expansion, we find that in a spherical expansion the system reaches the "out" regime much faster and more particles get produced. However the size of the unstable region, which is related to the domain size of DCCs, is not enhanced.

A model for the very early universe

Journal of High Energy Physics, 2008

A model with N species of massless fermions interacting via (microscopic) gravitational torsion in de Sitter spacetime is investigated in the limit N → ∞. The U V (N ) × U A (N ) flavor symmetry is broken dynamically irrespective of the (positive) value of the induced four-fermion coupling. This model is equivalent to a theory with free but massive fermions fluctuating about the chiral condensate. When the fermions are integrated out in a way demonstrated long ago by Candelas and Raine, the associated gap equation together with the Friedmann equation predict that the Hubble parameter vanishes. Introducing a matter sector (subject to a finite gauge symmetry) as a source for subsequent cosmology, the neutral Goldstone field acquires mass by the chiral anomaly, resulting in a Planck-scale axion.

Volume and quark mass dependence of the chiral phase transition

Physical Review D, 2006

We investigate chiral symmetry restoration in finite spatial volume and at finite temperature by calculating the dependence of the chiral phase transition temperature T c on the size of the spatial volume and the current-quark mass for the quark-meson model, using the proper-time Renormalization Group approach. We find that the critical temperature is weakly dependent on the size of the spatial volume for large current-quark masses, but depends strongly on it for small current-quark masses. In addition, for small volumes we observe a dependence on the choice of quark boundary conditions.

Relics of cosmological quark-hadron phase transition

Physical Review D, 2001

We propose that the amplified density fluctuations by the vanishing sound velocity effect during the cosmological quark-hadron phase transition lead to quark-gluon plasma lumps decoupled from the expansion of the universe, which may evolve to quark nuggets (QNs). Assuming power-law spectrum of density fluctuations, we investigate the parameter ranges for the QNs to play the role of baryonic dark matter and give inhomogeneities which could affect big-bang nucleosynthesis within the observational bounds of CMBR anisotropy. The QNs can give the strongest constraint ever found on the spectral index.