13,734 research outputs found
Variational Approach to the Chiral Phase Transition in the Linear Sigma Model
The chiral phase transition at finite temperature is investigated in the
linear sigma model, which is regarded as a low energy effective theory of QCD
with three momentum cutoff, in the variational method with the Gaussian
approximation in the functional Schroedinger picture. It is shown that the
Goldstone theorem is retained and the meson pair excitations are automatically
included by taking into account the linear response to the external fields. It
is pointed out that the behavior of chiral phase transition depends on the
three-momentum cutoff, which leads to the careful treatment of the problem.Comment: 14 pages, 5 figures, using PTPTeX cl
Remote Inflation: Hybrid-like inflation without hybrid-type potential
A new scenario of hybrid-like inflation is considered without using
hybrid-type potential. Radiation raised continuously by a dissipating inflaton
field keeps symmetry restoration in a remote sector, and the false-vacuum
energy of the remote sector dominates the energy density during inflation.
Remote inflation is terminated when the temperature reaches the critical
temperature, or when the slow-roll condition is violated. Without introducing a
complex form of couplings, inflaton field may either roll-in (like a standard
hybrid inflation) or roll-out (like an inverted-hybrid model or quintessential
inflation) on arbitrary inflaton potential. Significant signatures of remote
inflation can be observed in the spectrum caused by (1) the inhomogeneous phase
transition in the remote sector, or (2) a successive phase transition in the
remote sector. Remote inflation can predict strong amplification or suppression
of small-scale perturbations without introducing multiple inflation. Since the
inflaton may have a run-away potential, it is also possible to identify the
inflaton with quintessence, without introducing additional mechanisms. Even if
the false-vacuum energy is not dominated by the remote sector, the phase
transition in the remote sector is possible during warm inflation, which may
cause significant amplification/suppression of the curvature perturbations.Comment: 28 pages, 1 figure, fixed references, accepted for publication in
JCA
Flux Line Lattice Melting and the Formation of a Coherent Quasiparticle Bloch State in the Ultraclean URuSi Superconductor
We find that in ultraclean heavy-fermion superconductor URuSi
( K) a distinct flux line lattice melting transition with
outstanding characters occurs well below the mean-field upper critical fields.
We show that a very small number of carriers with heavy mass in this system
results in exceptionally large thermal fluctuations even at subkelvin
temperatures, which are witnessed by a sizable region of the flux line liquid
phase. The uniqueness is further highlighted by an enhancement of the
quasiparticle mean free path below the melting transition, implying a possible
formation of a quasiparticle Bloch state in the periodic flux line lattice.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. Let
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