Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOn the dynamics of phase transitions and the nonequilibrium formation of topological defects
53
0
0.0
(
0
)
Added by
Gregory James Stephens
Publication date
2001
fields
Physics
and research's language is
English
Authors
G. J. Stephens
Ask ChatGPT about the research
No Arabic abstract
We study the formation of topological defects in nonequilibrium phase transitions of both classical and quantum field theory. We examine three model systems. 1). The phase transition of a quantum scalar field in a FRW universe is analyzed through a first-principles approach in which the dynamics of the two-point function is derived from the two-loop, two-particle-irreducible closed-time-path effective action. Identifying signatures of correlated domains in the infrared portion of the momentum-space power spectrum we find that the domain size scales as a power-law with the expansion rate of the universe. The observed power-law scaling is in good agreement with the predictions of the Kibble-Zurek mechanism of defect formation and provides evidence of the freeze-out scenario in the context of nonequilibrium quantum field theory. 2). The formation and interaction of topological textures is analyzed in the phase transition of a classical O(3) scalar field theory in 2+1 dimensions. We provide quantiive arguments that by the end of the transition the length scales of the texture distribution result from a competition between the length scale determined at freeze-out and the ordering dynamics of a textured system. 3). We discuss a black hole phase transition in semiclassical gravity. We review the thermodynamics of a black hole system and determine that the phase transition is entropically driven. We introduce a quantum atomic model of the equilibrium black hole system and show that the phase transition is realized as the abrupt excitation of a high energy state. We investigate the nonequilibrium dynamics of the black hole phase transition and explore similar examples from the Kosterlitz-Thouless transition in condensed matter to the Hagedorn transition in string theory.
rate research
Read More
The evolution of the Universe is the ultimate laboratory to study fundamental physics across energy scales that span about 25 orders of magnitude: from the grand unification scale through particle and nuclear physics scales down to the scale of atomic physics. The standard models of cosmology and particle physics provide the basic understanding of the early and present Universe and predict a series of phase transitions that occurred in succession during the expansion and cooling history of the Universe. We survey these phase transitions, highlighting the equilibrium and non-equilibrium effects as well as their observational and cosmological consequences. We discuss the current theoretical and experimental programs to study phase transitions in QCD and nuclear matter in accelerators along with the new results on novel states of matter as well as on multi- fragmentation in nuclear matter. A critical assessment of similarities and differences between the conditions in the early universe and those in ultra- relativistic heavy ion collisions is presented. Cosmological observations and accelerator experiments are converging towards an unprecedented understanding of the early and present Universe.
Using 3+1 classical lattice simulations, we follow the symmetry breaking pattern and subsequent non-linear evolution of a spectator field non-minimally coupled to gravity when the post-inflationary dynamics is given in terms of a stiff equation-of-state parameter. We find that the gradient energy density immediately after the transition represents a non-negligible fraction of the total energy budget, steadily growing to equal the kinetic counterpart. This behaviour is reflected on the evolution of the associated equation-of-state parameter, which approaches a universal value $1/3$, independently of the shape of non-linear interactions. Combined with kination, this observation allows for the generic onset of radiation domination for arbitrary self-interacting potentials, significantly extending previous results in the literature. The produced spectrum at that time is, however, non-thermal, precluding the naive extraction of thermodynamical quantities like temperature. Potential identifications of the spectator field with the Standard Model Higgs are also discussed.
We consider quantum phase transitions with global symmetry breakings that result in the formation of topological defects. We evaluate the number densities of kinks, vortices, and monopoles that are produced in $d=1,2,3$ spatial dimensions respectively and find that they scale as $t^{-d/2}$ and evolve towards attractor solutions that are independent of the quench timescale. For $d=1$ our results apply in the region of parameters $lambda tau/m ll 1$ where $lambda$ is the quartic self-interaction of the order parameter, $tau$ is the quench timescale, and $m$ the mass parameter.
We point out that in models of macroscopic topological defects composed of one or more scalar fields that interact with standard-model fields via scalar-type couplings, the back-action of ambient matter on the scalar field(s) produces an environmental dependence of the fundamental constants of nature, as well as spatial variations of the fundamental constants in the vicinity of dense bodies such as Earth due to the formation of a bubble-like defect structure surrounding the dense body. In sufficiently dense environments, spontaneous symmetry breaking may be inhibited altogether for $phi^2$ interactions, potentially delaying the cosmological production of topological defects. We derive bounds on non-transient variations of the fundamental constants from torsion-pendulum experiments that search for equivalence-principle-violating forces, experiments comparing the frequencies of ground- and space-based atomic clocks, as well as ground-based clocks at different heights in the recent Tokyo Skytree experiment, and measurements comparing atomic and molecular transition frequencies in terrestrial and low-density astrophysical environments. Our results constrain the present-day mass-energy fraction of the Universe due to a network of infinite domain walls produced shortly after the BBN or CMB epochs to be $Omega_{textrm{walls},0} ll 10^{-10}$ for the symmetron model with a $phi^4$ potential and $phi^2$ interactions, improving over CMB quadrupolar temperature anisotropy bounds by at least 5 orders of magnitude. Our newly derived bounds on domain walls with $phi^2$ interactions via their effects of non-transient variations of the fundamental constants are significantly more stringent than previously reported clock- and cavity-based limits on passing domain walls via transient signatures and previous bounds from different types of non-transient signatures, under the same set of assumptions.
Gravitational waves generated during a first-order electroweak phase transition have a typical frequency which today falls just within the band of the planned space interferometer LISA. Contrary to what happens in the Standard Model, in its supersymmetric extensions the electroweak phase transition may be strongly first order, providing a mechanism for generating the observed baryon asymmetry in the Universe. We show that during the same transition the production of gravitational waves can be rather sizable. While the energy density in gravitational waves can reach at most $h_0^2 Omega_{rm gw}simeq 10^{-16}$ in the Minimal Supersymmetric Standard Model, in the Next-to-Minimal Supersymmetric Model, in some parameter range, $h_0^2 Omega_{rm gw}$ can be as high as $4times 10^{-11}$. A stochastic background of gravitational waves of this intensity is within the reach of the planned sensitivity of LISA. Since in the Standard Model the background of gravitational waves is totally neglegible, its detection would also provide a rather unexpected experimental signal of supersymmetry and a tool to descriminate among supersymmetric models with different Higgs content.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
