9,047 research outputs found
The energy of the high-temperature quark-gluon plasma
For the quark-gluon plasma, an energy-momentum tensor is found corresponding
to the high-temperature Braaten-Pisarski effective action. The tensor is found
by considering the interaction of the plasma with a weak gravitational field
and the positivity of the energy is studied. In addition, the complete
effective action in curved spacetime is written down.Comment: 13 pages, one figure, plain TeX forma
Comparing the effects of hypothetical moral preferences on real-life and hypothetical behavior:Commentary on Bostyn, Sevenhant, and Roets (2018)
Keywords: consequentialism, morality, trolley, utilitarianis
Finite Temperature Effective Actions
We present, from first principles, a direct method for evaluating the exact
fermion propagator in the presence of a general background field at finite
temperature, which can be used to determine the finite temperature effective
action for the system. As applications, we determine the complete one loop
finite temperature effective actions for 0+1 dimensional QED as well as the
Schwinger model. These effective actions, which are derived in the real time
(closed time path) formalism, generate systematically all the Feynman
amplitudes calculated in thermal perturbation theory and also show that the
retarded (advanced) amplitudes vanish in these theories.Comment: 5 pages, revtex, typos fixed, references added, to be published in
Physics Letters
Nebraska Extension educators bring entrepreneurship education to Georgia and Armenia
In a unique initiative by the American Councils for International Education, Nebraska Extension educators Molly Brandt and Marilyn Schlake were invited to travel to the countries of Georgia and Armenia in 2022 to train local educators in the principles of the 4-H Entrepreneurship Investigation (ESI) curriculum.
Brandt, an innovation and entrepreneurship 4-H educator, and Schlake, a Rural Prosperity Nebraska educator in the Department of Agricultural Economics, prepared for what they thought was a one-time experience. However, after their successful endeavor in Tbilisi, Georgia, in October 2022, they were invited back in April 2023, to deliver similar training in Yerevan, Armenia
Variational Inequalities in Critical-State Problems
Similar evolutionary variational inequalities appear as convenient
formulations for continuous quasistationary models for sandpile growth,
formation of a network of lakes and rivers, magnetization of type-II
superconductors, and elastoplastic deformations. We outline the main steps of
such models derivation and try to clarify the origin of this similarity. New
dual variational formulations, analogous to mixed variational inequalities in
plasticity, are derived for sandpiles and superconductors.Comment: Submitted for publicatio
Symmetry without Symmetry: Numerical Simulation of Axisymmetric Systems using Cartesian Grids
We present a new technique for the numerical simulation of axisymmetric
systems. This technique avoids the coordinate singularities which often arise
when cylindrical or polar-spherical coordinate finite difference grids are
used, particularly in simulating tensor partial differential equations like
those of 3+1 numerical relativity. For a system axisymmetric about the z axis,
the basic idea is to use a 3-dimensional Cartesian (x,y,z) coordinate grid
which covers (say) the y=0 plane, but is only one
finite-difference-molecule--width thick in the y direction. The field variables
in the central y=0 grid plane can be updated using normal (x,y,z)--coordinate
finite differencing, while those in the y \neq 0 grid planes can be computed
from those in the central plane by using the axisymmetry assumption and
interpolation. We demonstrate the effectiveness of the approach on a set of
fully nonlinear test computations in 3+1 numerical general relativity,
involving both black holes and collapsing gravitational waves.Comment: 17 pages, 4 figure
Return of the lysergamides. Part III: Analytical characterization of N6-ethyl-6-norlysergic acid diethylamide (ETH-LAD) and 1-propionyl ETH-LAD (1P-ETH-LAD)
The psychoactive properties of lysergic acid diethylamide (LSD) have fascinated scientists across disciplines and the exploration of other analogs and derivatives has been motivated by deepening the understanding of ligand-receptor interactions at the molecular level as well as by the search for new therapeutics. Several LSD congeners have appeared on the new psychoactive substances (NPS) market in the form of blotters or powders. Examples include 1-propionyl-LSD (1P-LSD), AL-LAD and LSZ. The absence of analytical data for novel compounds is a frequent challenge encountered in clinical and toxicological investigations. Two newly emerging lysergamides N6-ethyl-6-norlysergic acid diethylamide (ETH-LAD) and 1P-ETH-LAD were characterized by gas chromatography mass spectrometry (GC-MS), low and high mass accuracy electrospray MS(/MS), GC solid-state infrared analysis, high performance liquid chromatography diode array detection as well as nuclear magnetic resonance spectroscopy. Limited analytical data for ETH-LAD were previously available, whereas information about 1P-ETH-LAD has not previously been encountered in scientific literature. This study extends the characterization of lysergamides distributed on the NPS market, which will help to make analytical data available to clinicians, toxicologists and other stakeholders who are likely to encounter these substances. The analysis of a test incubation of 1P-ETH-LAD with human serum at 37°C by LC single quadrupole MS at various time points (0–6 h, once per hour and one measurement after 24 h) revealed the formation of ETH-LAD, suggesting that 1P-ETH-LAD might serve as a pro-drug. 1P-ETH-LAD was still detectable in serum after 24 h
Numerical investigation of the partial oxidation in a two-stage downdraft gasifyer
International audienceno abstrac
Retarded Greens Functions and Forward Scattering Amplitudes in Thermal Field Theory
In this paper, we give a simple diagrammatic identification of the unique
combination of the causal n-point vertex functions in the real time formalism
that would coincide with the corresponding functions obtained in the imaginary
time formalism. Furthermore, we give a simple calculational method for
evaluating the temperature dependent parts of the retarded vertex functions, to
one loop, by identifying them with the forward scattering amplitudes of
on-shell thermal particles. As an application of the method, we calculate and
show that the temperature dependent parts of all the retarded functions vanish
at one loop order for 1+1 dimensional massless QED. We further point out that,
in this model, in fact, the temperature dependent parts of all the retarded
vertex functions vanish to all orders in perturbation theory.Comment: 10 pages and figures in the eepic forma
An operator representation for Matsubara sums
In the context of the imaginary-time formalism for a scalar thermal field
theory, it is shown that the result of performing the sums over Matsubara
frequencies associated with loop Feynman diagrams can be written, for some
classes of diagrams, in terms of the action of a simple linear operator on the
corresponding energy integrals of the Euclidean theory at T=0. In its simplest
form the referred operator depends only on the number of internal propagators
of the graph.
More precisely, it is shown explicitly that this \emph{thermal operator
representation} holds for two generic classes of diagrams, namely, the
two-vertex diagram with an arbitrary number of internal propagators, and the
one-loop diagram with an arbitrary number of vertices.
The validity of the thermal operator representation for diagrams of more
complicated topologies remains an open problem. Its correctness is shown to be
equivalent to the correctness of some diagrammatic rules proposed a few years
ago.Comment: 4 figures; references added, minor changes in notation, final version
accepted for publicatio
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