355 research outputs found
Dual PT-Symmetric Quantum Field Theories
Some quantum field theories described by non-Hermitian Hamiltonians are
investigated. It is shown that for the case of a free fermion field theory with
a mass term the Hamiltonian is -symmetric. Depending on the
mass parameter this symmetry may be either broken or unbroken. When the symmetry is unbroken, the spectrum of the quantum field theory is real. For
the -symmetric version of the massive Thirring model in
two-dimensional space-time, which is dual to the -symmetric scalar
Sine-Gordon model, an exact construction of the operator is given. It
is shown that the -symmetric massive Thirring and Sine-Gordon models
are equivalent to the conventional Hermitian massive Thirring and Sine-Gordon
models with appropriately shifted masses.Comment: 9 pages, 1 figur
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Applications of Solid Freeform Fabrication at the Naval Research Laboratory
Solid Freeform Fabrication (SFF) and related techniques are used at the Naval Research
Laboratory (NRL) for a variety of materials related investigations. Research and applications
conducted over the past few years are described including: Helisys Laminated Object
Manufacturing System (LOMS) fabrication of: ceramic piezoelectric actuators, tooling for
multifunctional materials, and anatomical prototypes for surgical visualization; fabrication of
mesoscale electronic and sensor components using a laser forward transfer direct write
technique; and visualization of complex, 3-D microstructures using a Stratasys Fused-Deposition
Modeler. The paper closes with a brief overview of future SFF related work at the NRL.Support for this work from DARPA, Office of Naval Research, and the Naval Research
Laboratory Core Research Program is gratefully acknowledged.Mechanical Engineerin
Single-Particle Properties from Kohn-Sham Green's Functions
An effective action approach to Kohn-Sham density functional theory is used
to illustrate how the exact Green's function can be calculated in terms of the
Kohn-Sham Green's function. An example based on Skyrme energy functionals shows
that single-particle Kohn-Sham spectra can be improved by adding sources used
to construct the energy functional.Comment: 9 pages, 3 figure
Resummation of Nonalternating Divergent Perturbative Expansions
A method for the resummation of nonalternating divergent perturbation series
is described. The procedure constitutes a generalization of the Borel-Pad\'{e}
method. Of crucial importance is a special integration contour in the complex
plane. Nonperturbative imaginary contributions can be inferred from the purely
real perturbative coefficients. A connection is drawn from the quantum field
theoretic problem of resummation to divergent perturbative expansions in other
areas of physics.Comment: 5 pages, LaTeX, 2 tables, 1 figure; discussion of the Carleman
criterion added; version to appear in Phys. Rev.
Nuclear Ground State Observables and QCD Scaling in a Refined Relativistic Point Coupling Model
We present results obtained in the calculation of nuclear ground state
properties in relativistic Hartree approximation using a Lagrangian whose
QCD-scaled coupling constants are all natural (dimensionless and of order 1).
Our model consists of four-, six-, and eight-fermion point couplings (contact
interactions) together with derivative terms representing, respectively, two-,
three-, and four-body forces and the finite ranges of the corresponding mesonic
interactions. The coupling constants have been determined in a self-consistent
procedure that solves the model equations for representative nuclei
simultaneously in a generalized nonlinear least-squares adjustment algorithm.
The extracted coupling constants allow us to predict ground state properties of
a much larger set of even-even nuclei to good accuracy. The fact that the
extracted coupling constants are all natural leads to the conclusion that QCD
scaling and chiral symmetry apply to finite nuclei.Comment: 44 pages, 13 figures, 9 tables, REVTEX, accepted for publication in
Phys. Rev.
Quantum Extremism: Effective Potential and Extremal Paths
The reality and convexity of the effective potential in quantum field
theories has been studied extensively in the context of Euclidean space-time.
It has been shown that canonical and path-integral approaches may yield
different results, thus resolving the `convexity problem'. We discuss the
transferral of these treatments to Minkowskian space-time, which also
necessitates a careful discussion of precisely which field configurations give
the dominant contributions to the path integral. In particular, we study the
effective potential for the N=1 linear sigma model.Comment: 11 pages, 4 figure
Pasts and pagan practices: moving beyond Stonehenge
Theorizing the past is not restricted to archaeology and interpretations of 'past' both influence and are themselves constituted within politicized understandings of self, community and in certain instances, spirituality. 'The past in the imagination of the present' is appropriated, variously, to give meaning to the present or to justify actions and interpret experiences. Summer solstice at Stonehenge, with an estimated 21,000 celebrants in 2005, is only the most publicized appropriation (by pagans and other adherents of alternative spirituality and partying) of a 'sacred site'; and conflicts and negotiations occurring throughout Britain are represented in popular and academic presentations of this 'icon of Britishness'. This paper presents work from the Sacred Sites, Contested Rites/Rights Project (http://www.sacredsites.org.uk) project, a collaboration of archaeology and anthropology informed by pagan and alternative approaches and standpoints investigating and theorizing discourse and practice of heritage management and pagan site users. Whether in negotiations around the Stonehenge solstice access or in dealing with numerous other sites, boundaries between groups or discourses are not clearly drawn - discursive communities merge and re-emerge. But clearly 'past' and 'site' are increasingly important within today's Britain, even as television archaeology increases its following, and pagan numbers continue to grow.</p
Effect of tensor couplings in a relativistic Hartree approach for finite nuclei
The relativistic Hartree approach describing the bound states of both
nucleons and anti-nucleons in finite nuclei has been extended to include tensor
couplings for the - and -meson. After readjusting the parameters
of the model to the properties of spherical nuclei, the effect of
tensor-coupling terms rises the spin-orbit force by a factor of 2, while a
large effective nucleon mass sustains. The overall
nucleon spectra of shell-model states are improved evidently. The predicted
anti-nucleon spectra in the vacuum are deepened about 20 -- 30 MeV.Comment: 31 pages, 4 postscript figures include
Effective Field Theory for Dilute Fermions with Pairing
Effective field theory (EFT) methods for a uniform system of fermions with
short-range, natural interactions are extended to include pairing correlations,
as part of a program to develop a systematic Kohn-Sham density functional
theory (DFT) for medium and heavy nuclei. An effective action formalism for
local composite operators leads to a free-energy functional that includes
pairing by applying an inversion method order by order in the EFT expansion. A
consistent renormalization scheme is demonstrated for the uniform system
through next-to-leading order, which includes induced-interaction corrections
to pairing.Comment: 31 pages, 10 figures, affiliation updated, paper unchange
A Grand Canonical Ensemble Approach to the Thermodynamic Properties of the Nucleon in the Quark-Gluon Coupling Model
In this paper, we put forward a way to study the nucleon's thermodynamic
properties such as its temperature, entropy and so on, without inputting any
free parameters by human hand, even the nucleon's mass and radius. First we use
the Lagrangian density of the quark gluon coupling fields to deduce the Dirac
Equation of the quarks confined in the gluon fields. By boundary conditions we
solve the wave functions and energy eigenvalues of the quarks, and thus get
energy-momentum tensor, nucleon mass, and density of states. Then we utilize a
hybrid grand canonical ensemble, to generate the temperature and chemical
potentials of quarks, antiquarks of three flovars by the four conservation laws
of the energy and the valence quark numbers, after which, all other
thermodynamic properties are known. The only seemed free paremeter, the nucleon
radius is finally determined by the grand potential minimal principle.Comment: 5 pages, LaTe
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