11,612 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
Elliptic Inflation: Generating the curvature perturbation without slow-roll
There are many inflationary models in which inflaton field does not satisfy
the slow-roll condition. However, in such models, it is always difficult to
generate the curvature perturbation during inflation. Thus, to generate the
curvature perturbation, one must introduce another component to the theory. To
cite a case, curvatons may generate dominant part of the curvature perturbation
after inflation. However, we have a question whether it is unrealistic to
consider the generation of the curvature perturbation during inflation without
slow-roll. Assuming multi-field inflation, we encounter the generation of the
curvature perturbation during inflation without slow-roll. The potential along
equipotential surface is flat by definition and thus we do not have to worry
about symmetry. We also discuss about KKLT models, in which corrections lifting
the inflationary direction may not become a serious problem if there is a
symmetry enhancement at the tip (not at the moving brane) of the inflationary
throat.Comment: 27pages, 8figures, to appear in JCA
Diffuse Lyman Alpha Haloes around Lyman Alpha Emitters at z=3: Do Dark Matter Distributions Determine the Lyman Alpha Spatial Extents?
Using stacks of Ly-a images of 2128 Ly-a emitters (LAEs) and 24 protocluster
UV-selected galaxies (LBGs) at z=3.1, we examine the surface brightness
profiles of Ly-a haloes around high-z galaxies as a function of environment and
UV luminosity. We find that the slopes of the Ly-a radial profiles become
flatter as the Mpc-scale LAE surface densities increase, but they are almost
independent of the central UV luminosities. The characteristic exponential
scale lengths of the Ly-a haloes appear to be proportional to the square of the
LAE surface densities (r(Lya) \propto Sigma(LAE)^2). Including the diffuse,
extended Ly-a haloes, the rest-frame Ly-a equivalent width of the LAEs in the
densest regions approaches EW_0(Lya) ~ 200 A, the maximum value expected for
young (< 10^7 yr) galaxies. This suggests that Ly-a photons formed via shock
compression by gas outflows or cooling radiation by gravitational gas inflows
may partly contribute to illuminate the Ly-a haloes; however, most of their
Ly-a luminosity can be explained by photo-ionisation by ionising photons or
scattering of Ly-a photons produced in HII regions in and around the central
galaxies. Regardless of the source of Ly-a photons, if the Ly-a haloes trace
the overall gaseous structure following the dark matter distributions, it is
not surprising that the Ly-a spatial extents depend more strongly on the
surrounding Mpc-scale environment than on the activities of the central
galaxies.Comment: 7 pages, 4 figures, accepted for publication in MNRA
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