493 research outputs found
Mass Expansions of Screened Perturbation Theory
The thermodynamics of massless phi^4-theory is studied within screened
perturbation theory (SPT). In this method the perturbative expansion is
reorganized by adding and subtracting a mass term in the Lagrangian. We
analytically calculate the pressure and entropy to three-loop order and the
screening mass to two-loop order, expanding in powers of m/T. The truncated
m/T-expansion results are compared with numerical SPT results for the pressure,
entropy and screening mass which are accurate to all orders in m/T. It is shown
that the m/T-expansion converges quickly and provides an accurate description
of the thermodynamic functions for large values of the coupling constant.Comment: 22 pages, 10 figure
Pressure to order in -theory at weak coupling
We calculate the pressure of massless -theory to order
at weak coupling. The contributions to the pressure arise from the hard
momentum scale of order and the soft momentum scale of order .
Effective field theory methods and dimensional reduction are used to separate
the contributions from the two momentum scales: The hard contribution can be
calculated as a power series in using naive perturbation theory with bare
propagators. The soft contribution can be calculated using an effective theory
in three dimensions, whose coefficients are power series in . This
contribution is a power series in starting at order . The calculation
of the hard part to order involves a complicated four-loop sum-integral
that was recently calculated by Gynther, Laine, Schr\"oder, Torrero, and
Vuorinen. The calculation of the soft part requires calculating the mass
parameter in the effective theory to order and the evaluation of
five-loop vacuum diagrams in three dimensions. This gives the free energy
correct up to order . The coefficients of the effective theory satisfy a
set of renormalization group equations that can be used to sum up leading and
subleading logarithms of . We use the solutions to these equations to
obtain a result for the free energy which is correct to order .
Finally, we investigate the convergence of the perturbative series.Comment: 29 pages and 12 figs. New version: we have pushed the calculations to
g^8*log(g) using the renormalization group to sum up log(g) from higher
orders. Published in JHE
Screened Perturbation Theory to Three Loops
The thermal physics of a massless scalar field with a phi^4 interaction is
studied within screened perturbation theory (SPT). In this method the
perturbative expansion is reorganized by adding and subtracting a mass term in
the lagrangian. We consider several different mass prescriptions that
generalize the one-loop gap equation to two-loop order. We calculate the
pressure and entropy to three-loop order and the screening mass to two-loop
order. In contrast to the weak-coupling expansion, the SPT-improved
approximations appear to converge even for rather large values of the coupling
constant.Comment: 30 pages, 10 figure
Three-loop HTL gluon thermodynamics at intermediate coupling
We calculate the thermodynamic functions of pure-glue QCD to three-loop order
using the hard-thermal-loop perturbation theory (HTLpt) reorganization of
finite temperature quantum field theory. We show that at three-loop order
hard-thermal-loop perturbation theory is compatible with lattice results for
the pressure, energy density, and entropy down to temperatures .
Our results suggest that HTLpt provides a systematic framework that can used to
calculate static and dynamic quantities for temperatures relevant at LHC.Comment: 24 pages, 13 figs. 2nd version: improved discussion and fixing typos.
Published in JHE
Thermal Effects in Low-Temperature QED
QED is studied at low temperature (, where is the electron mass)
and zero chemical potential. By integrating out the electron field and the
nonzero bosonic Matsubara modes, we construct an effective three-dimensional
field theory that is valid at distances . As applications, we
reproduce the ring-improved free energy and calculate the Debye mass to order
.Comment: 20 pages, 4 figures, revte
Polymeric strontium ranelate nonahydrate
The title compound, poly[[μ-aqua-tetraaqua{μ-5-[bis(carboxylatomethyl)amino]-3-carboxylatomethyl-4-cyanothiophene-2-carboxylato}distrontium(II)] tetrahydrate], [Sr2(C12H6N2O8S)(H2O)5]·3.79H2O, crystallizes with nine- and eight-coordinated Sr2+ cations. They are bound to seven of the eight ranelate O atoms and five of the water molecules. The SrO8 and SrO9 polyhedra are interconnected by edge-sharing, forming hollow layers parallel to (011). The layers are, in turn, interconnected by ranelate anions, forming a metal–organic framework (MOF) structure with channels along the a axis. The four water molecules not coordinated to strontium are located in these channels and hydrogen bonded to each other and to the ranelates. Part of the water H atoms are disordered. The compound dehydrates very easily and 0.210 (4) water molecules out of nine were lost during crystal mounting causing additional disorder in the water structure
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