233 research outputs found
The Landau Pole at Finite Temperature
We study the Landau pole in the lambda phi^4 field theory at non-zero and
large temperatures. We show that the position of the thermal Landau pole
Lambda_L(T) is shifted to higher energies with respect to the zero temperature
Landau pole Lambda_L(0). We find for high temperatures T > Lambda_L(0),
Lambda_L(T) simeq pi^2 T / log (T / Lambda_L(0)). Therefore, the range of
applicability in energy of the lambda phi^4 field theory increases with the
temperature.Comment: LaTex, 6 pages, 2 .ps figures. Improved version. To appear in Phys.
Rev. D, Rapid Communication
Critical region of the finite temperature chiral transition
We study a Yukawa theory with spontaneous chiral symmetry breaking and with a
large number N of fermions near the finite temperature phase transition.
Critical properties in such a system can be described by the mean field theory
very close to the transition point. We show that the width of the region where
non-trivial critical behavior sets in is suppressed by a certain power of 1/N.
Our Monte Carlo simulations confirm these analytical results. We discuss
implications for the chiral phase transition in QCD.Comment: 18 page
Kosterlitz-Thouless Universality in a Fermionic System
A new extension of the attractive Hubbard model is constructed to study the
critical behavior near a finite temperature superconducting phase transition in
two dimensions using the recently developed meron-cluster algorithm. Unlike
previous calculations in the attractive Hubbard model which were limited to
small lattices, the new algorithm is used to study the critical behavior on
lattices as large as . These precise results for the first time
show that a fermionic system can undergo a finite temperature phase transition
whose critical behavior is well described by the predictions of Kosterlitz and
Thouless almost three decades ago. In particular it is confirmed that the
spatial winding number susceptibility obeys the well known predictions of
finite size scaling for and up to logarithmic corrections the pair
susceptibility scales as at large volumes with for .Comment: Revtex format; 4 pages, 2 figure
Phase Structure of QED3 at Finite Temperature
Dynamical symmetry breaking in three-dimensional QED with N fermion flavours
is considered at finite temperature, in the large approximation. Using an
approximate treatment of the Schwinger-Dyson equation for the fermion
self-energy, we find that chiral symmetry is restored above a certain critical
temperature which depends itself on . We find that the ratio of the
zero-momentum zero-temperature fermion mass to the critical temperature has a
large value compared with four-fermion theories, as had been suggested in a
previous work with a momentum-independent self-energy. Evidence of a
temperature- dependent critical is shown to appear in this approximation.
The phase diagram for spontaneous mass generation in the theory is presented in
space.Comment: 9 page
Uv light impact on phthalates migration from children's toys into artificial saliva
Phthalates has been widely used in children?s toys as plastic plasticizers and softeners. Therefore, attention should be paid to plastic toys, especially those that children can put in their mouths. In this paper quantification of five phthalates: DMP, DnBP, BBP, DEHP and DnOP in plastic toys, as well as irradiation of toys with UV light was performed. After sample preparation and development of the liquid?liquid phthalate extraction method from artificial saliva phthalate quantitative determination using the GC?MS technique was performed. The mean recovery value for DEHP is 77.03?2.76 %. The determination of phthalate in the recipient models (artificial saliva and n-hexane) was performed after 6, 15 and 30 days of the migration test using the GC?MS technique. Based on the known mass % DEHP in the analyzed toys, the percentage of phthalate migration from each analyzed toy to the recipient model after 6, 15 and 30 days of the migration test was calculated. The results show that there is no significant migration of DEHP into artificial saliva, due to high polarity of the recipient (artificial saliva is polar), unlike n-hexane where the migration of DEHP is significant because it is a non-polar solvent
On the Interplay of Monopoles and Chiral Symmetry Breaking in Non-Compact Lattice QED
Non-compact lattice QED is simulated for various numbers of fermion species
ranging from 8 through 40 by the exact Hybrid Monte Carlo algorithm. Over
this range of , chiral symmetry breaking is found to be strongly
correlated with the effective monopoles in the theory. For between 8 and
16 the chiral symmetry breaking and monopole percolation transitions are second
order and coincident. Assuming powerlaw critical behavior, the correlation
length exponent for the chiral transition is identical to that of monopole
percolation. This result supports the conjecture that monopole percolation
``drives" the nontrivial chiral transition. For between 20 and 32, the
monopoles experience a first order condensation transition coincident with a
first order chiral transition. For as large as 40 both transitions are
strongly suppressed. The data at large N_f (N_f \mathrel {\mathpalette \vereq
>} 20) is interpreted in terms of a strongly interacting monopole gas-liquid
transition.Comment: Revtex file, 23 pages, hardcopy figures only
Dimensional Reduction and Quantum-to-Classical Reduction at High Temperatures
We discuss the relation between dimensional reduction in quantum field
theories at finite temperature and a familiar quantum mechanical phenomenon
that quantum effects become negligible at high temperatures. Fermi and Bose
fields are compared in this respect. We show that decoupling of fermions from
the dimensionally reduced theory can be related to the non-existence of
classical statistics for a Fermi field.Comment: 11 pages, REVTeX, revised v. to be published in Phys. Rev. D: some
points made more explici
On the Logarithmic Triviality of Scalar Quantum Electrodynamics
Using finite size scaling and histogram methods we obtain numerical results
from lattice simulations indicating the logarithmic triviality of scalar
quantum electrodynamics, even when the bare gauge coupling is chosen large.
Simulations of the non-compact formulation of the lattice abelian Higgs model
with fixed length scalar fields on lattices with ranging from
through indicate a line of second order critical points.
Fluctuation-induced first order transitions are ruled out. Runs of over ten
million sweeps for each produce specific heat peaks which grow
logarithmically with and whose critical couplings shift with picking
out a correlation length exponent of consistent with mean field
theory. This behavior is qualitatively similar to that found in pure
.Comment: 9 page
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