1,621 research outputs found
The Reeh-Schlieder property for thermal field theories
We show that the Reeh-Schlieder property w.r.t. the KMS-vector is a direct
consequence of locality, additivity and the relativistic KMS-condition. The
latter characterises the thermal equilibrium states of a relativistic quantum
field theory. The statement remains vaild even if the given equilibrium state
breaks spatial translation invariance.Comment: plain tex, 10 page
The Hot Bang state of massless fermions
In 2002, a method has been proposed by Buchholz et al. in the context of
Local Quantum Physics, to characterize states that are locally in thermodynamic
equilibrium. It could be shown for the model of massless bosons that these
states exhibit quite interesting properties. The mean phase-space density
satisfies a transport equation, and many of these states break time reversal
symmetry. Moreover, an explicit example of such a state, called the Hot Bang
state, could be found, which models the future of a temperature singularity.
However, although the general results carry over to the fermionic case easily,
the proof of existence of an analogue of the Hot Bang state is not quite that
straightforward. The proof will be given in this paper. Moreover, we will
discuss some of the mathematical subtleties which arise in the fermionic case.Comment: 17 page
Climatic, edaphic, and biotic controls over storage and turnover of carbon in soils
Soil carbon, a major component of the global carbon inventory, has significant potential for change with changing climate and human land use. We applied the Century ecosystem model to a series of forest and grassland sites distributed globally to examine large-scale controls over soil carbon. Key site-specific parameters influencing soil carbon dynamics are soil texture and foliar lignin content; accordingly, we perturbed these variables at each site to establish a range of carbon concentrations and turnover times. We examined the simulated soil carbon stores, turnover times, and C:N ratios for correlations with patterns of independent variables. Results showed that soil carbon is related linearly to soil texture, increasing as clay content increases, that soil carbon stores and turnover time are related to mean annual temperature by negative exponential functions, and that heterotrophic respiration originates from recent detritus (âŒ50%), microbial turnover (âŒ30%), and soil organic matter (âŒ20%) with modest variations between forest and grassland ecosystems. The effect of changing temperature on soil organic carbon (SOC) estimated by Century is dSOC/dT= 183eâ0.034T. Global extrapolation of this relationship leads to an estimated sensitivity of soil C storage to a temperature of â11.1 Pg° Câ1, excluding extreme arid and organic soils. In Century, net primary production (NPP) and soil carbon are closely coupled through the N cycle, so that as temperatures increase, accelerated N release first results in fertilization responses, increasing C inputs. The Century-predicted effect of temperature on carbon storage is modified by as much as 100% by the N cycle feedback. Century-estimated soil C sensitivity (â11.1 Pg° Câ1) is similar to losses predicted with a simple data-based calculation (â14.1 Pg° Câ1). Inclusion of the N cycle is important for even first-order predictions of terrestrial carbon balance. If the NPP-SOC feedback is disrupted by land use or other disturbances, then SOC sensitivity can greatly exceed that estimated in our simulations. Century results further suggest that if climate change results in drying of organic soils (peats), soil carbon loss rates can be high
Generalizations of the thermal Bogoliubov transformation
The thermal Bogoliubov transformation in thermo field dynamics is generalized
in two respects. First, a generalization of the --degree of freedom to
tilde non--conserving representations is considered. Secondly, the usual
Bogoliubov matrix is extended to a matrix including
mixing of modes with non--trivial multiparticle correlations. The analysis is
carried out for both bosons and fermions.Comment: 20 pages, Latex, Nordita 93/33
Role of anion size, magnetic moment, and disorder on the properties of the organic conductor kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}
Shubnikov-de Haas and angular dependent magnetoresistance oscillations have
been used to explore the role of anion size, magnetic moment, and disorder in
the organic conductors kappa-(BETS)_2GaBr_{4} and kappa-(BETS)_2FeCl_{2}_Br_{2}
in the isomorphic class kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}. The
results, combined with previous work, show correlations between the anion
composition (Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}) and the superconducting transition
temperature, effective mass, Fermi surface topology, and the mean free path.Comment: 5 pages, 6 figure
Successful Late Management of Esophageal Perforation with T-Tube Drainage
The late management of spontaneous esophageal perforation is the most challenging problem for the surgeon. In this paper, we present a case in whom a spontaneous esophageal perforation was successfully treated by T-tube drainage after unsuccessful conservative treatment. The patient, a 68-year-old male, was admitted to the hospital with sudden upper abdominal pain. After 2 days, esophageal perforation was diagnosed, and conservative management was begun. Thereafter, the subcutaneous emphysema disappeared, and the patient's temperature decreased. However, on day 13, the patient's temperature spiked above 38°C, and computed tomography showed a mediastinal abscess. An emergency left thoracotomy with laparotomy was performed. Since a 2-cm longitudinal perforation with severe inflammatory reactions was observed, the T-tube drainage method was performed. The patient was discharged without postoperative complications and has not experienced any gastrointestinal symptoms, such as gastroesophageal reflux or dysphagia. In conclusion, the T-tube drainage method appears to be a simple and effective method for the late management of esophageal perforation with severe inflammatory reaction
THERMAL EFFECTS ON THE CATALYSIS BY A MAGNETIC FIELD
We show that the formation of condensates in the presence of a constant
magnetic field in 2+1 dimensions is extremely unstable. It disappears as soon
as a heat bath is introduced with or without a chemical potential. We point out
some new nonanalytic behavior that develops in this system at finite
temperature.Comment: 10 pages, plain Te
Master Equations for Extended Lagrangian BRST Symmetries
Starting from the requirement that a Lagrangian field theory be invariant
under both Schwinger-Dyson BRST and Schwinger-Dyson anti-BRST symmetry, we
derive the BRST--anti-BRST analogue of the Batalin-Vilkovisky formalism. This
is done through standard Lagrangian gauge fixing respecting the extended BRST
symmetry. The solutions of the resulting Master Equation and the gauge-fixing
procedure for the quantum action can be brought into forms that coincide with
those obtained earlier on algebraic grounds by Batalin, Lavrov and Tyutin.Comment: 12 pages, LaTeX, KUL-TF-93/04 and CERN-TH-6800/9
Climate Change Impacts on Freshwater Wetland Hydrology and Vegetation Cover Cycling Along a Regional Aridity Gradient
Global mean temperature may increase up to 6°C by the end of this century and together with precipitation change may steepen regional aridity gradients. The hydrology, productivity, and ecosystem services from freshwater wetlands depend on their future water balance. We simulated the hydrology and vegetation dynamics of wetland complexes in the North American Prairie Pothole Region with the WETLANDSCAPE model. Simulations for 63 precipitation Ă temperature combinations spanning 6°C warming and â20% to +20% annual precipitation change at 19 locations along a mid-continental aridity gradient showed that aridity explained up to 99% of the variation in wetland stage and hydroperiod for all wetland permanence types, and in vegetation cycling for semipermanent wetlands. The magnitude and direction of hydrologic responses depended on whether climate changes increased or decreased water deficits. Warming to 6°C and 20% less precipitation increased wetland water deficits and more strongly decreased wetland stage and hydroperiod from historic levels at low aridity, especially in semipermanent wetlands, where peak vegetation cycling (Cover Cycle Index, CCI) also shifted to lower aridity. In contrast, 20% more precipitation decreased water deficits, increasing wetland stage and hydroperiod most strongly in shallow wetlands at high aridity, but filling semipermanent wetlands and reducing CCI at low aridity. All climate changes narrowed the range of aridity favorable to high productivity. Climate changes that reduce water deficits may help maintain wetlands at high aridity at the expense of those at low aridity, but with warming certain, increased deficits are more likely and will help maintain wetlands at lower aridity but exacerbate loss of wetlands at high aridity. Thus, there is likely not a universally applicable approach to mitigating climate change impacts on freshwater wetlands across regional aridity gradients. Conservation strategies need to account for aridity-specific effects of climate change on freshwater wetland ecosystems
QED symmetries in real-time thermal field theory
We study the discrete and gauge symmetries of Quantum Electrodynamics at
finite temperature within the real-time formalism.
The gauge invariance of the complete generating functional leads to the
finite temperature Ward identities. These Ward identities relate the eight
vertex functions to the elements of the self-energy matrix. Combining the
relations obtained from the and the gauge symmetries of the theory we
find that only one out of eight longitudinal vertex functions is independent.
As a consequence of the Ward identities it is shown that some elements of the
vertex function are singular when the photon momentum goes to zero.Comment: New version as it will appear in Phys RevD 19 pages, RevTex, 1figur
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