843 research outputs found
Towards a Nonperturbative Path Integral in Gauge Theories
We propose a modification of the Faddeev-Popov procedure to construct a path
integral representation for the transition amplitude and the partition function
for gauge theories whose orbit space has a non-Euclidean geometry. Our approach
is based on the Kato-Trotter product formula modified appropriately to
incorporate the gauge invariance condition, and thereby equivalence to the
Dirac operator formalism is guaranteed by construction. The modified path
integral provides a solution to the Gribov obstruction as well as to the
operator ordering problem when the orbit space has curvature. A few explicit
examples are given to illustrate new features of the formalism developed. The
method is applied to the Kogut-Susskind lattice gauge theory to develop a
nonperturbative functional integral for a quantum Yang-Mills theory. Feynman's
conjecture about a relation between the mass gap and the orbit space geometry
in gluodynamics is discussed in the framework of the modified path integral.Comment: plain Latex, 12 pages, a few changes made and some comments added, a
final version to appear in Phys. Lett.
Coordinate-Free Quantization of Second-Class Constraints
The conversion of second-class constraints into first-class constraints is
used to extend the coordinate-free path integral quantization, achieved by a
flat-space Brownian motion regularization of the coherent-state path integral
measure, to systems with second-class constraints.Comment: 21 pages, plain LaTeX, no figure
The Connection Between Diffuse Light and Intracluster Planetary Nebulae in the Virgo Cluster
We compare the distribution of diffuse intracluster light detected in the
Virgo Cluster via broadband imaging with that inferred from searches for
intracluster planetary nebulae (IPNe). We find a rough correspondence on large
scales (~ 100 kpc) between the two, but with very large scatter (~ 1.3
mag/arcsec^2). On smaller scales (1 -- 10 kpc), the presence or absence of
correlation is clearly dependent on the underlying surface brightness. On these
scales, we find a correlation in regions of higher surface brightness (mu_V <
~27) which are dominated by the halos of large galaxies such as M87, M86, and
M84. In those cases, we are likely tracing PNe associated with galaxies rather
than true IPNe. In true intracluster fields, at lower surface brightness, the
correlation between luminosity and IPN candidates is much weaker. While a
correlation between broadband light and IPNe is expected based on stellar
populations, a variety of statistical, physical, and methodological effects can
act to wash out this correlation and explain the lack of a strong correlation
at lower surface brightness found here. [abridged
Wave Propagation in Stochastic Spacetimes: Localization, Amplification and Particle Creation
Here we study novel effects associated with electromagnetic wave propagation
in a Robertson-Walker universe and the Schwarzschild spacetime with a small
amount of metric stochasticity. We find that localization of electromagnetic
waves occurs in a Robertson-Walker universe with time-independent metric
stochasticity, while time-dependent metric stochasticity induces exponential
instability in the particle production rate. For the Schwarzschild metric,
time-independent randomness can decrease the total luminosity of Hawking
radiation due to multiple scattering of waves outside the black hole and gives
rise to event horizon fluctuations and thus fluctuations in the Hawking
temperature.Comment: 26 pages, 1 Postscript figure, submitted to Phys. Rev. D on July 29,
199
Energy, Aesthetics and Knowledge in Complex Economic Systems
It is argued that the fact that economic systems are dissipative structures must be taken fully into account in economics if we are to understand the nature of the economic-ecological interface and how to deal with emergent environmental problems, such as global warming. Such problems are a product of economic growth, which is widely accepted to be the outcome of the acquisition and application of knowledge. Drawing upon disparate literatures within and outside economics, it is argued that economic growth should be more properly viewed as the outcome of a co-evolutionary process that involves the autocatalytic interaction of new knowledge and access of increasing amounts of free energy to do increasingly specialized forms of work. The conventional view is that energy is just a factor of production used increasingly as new knowledge is employed. The possibility of reverse causation is considered here. Specifically, the relevance of the ‘energy hypothesis,’ associated with Eric Schneider and his collaborators, is assessed. This hypothesis states that all dissipative structures have, as their primary objective, the reduction of accessible free energy gradients. It is concluded that such a hypothesis cannot be rejected in the context of economic behaviour and that this opens up an important research agenda for economists. It is argued that such research has to be interdisciplinary because our economic behaviour is driven by aspirational goals which are aesthetic constructions in the mind and strongly connected to our emotions. In this regard, recent neuropsychological literature, arguing that certain emotional dispositions are necessary before we can employ our cognitive capabilities effectively, is important to digest. Thus, the possibility exists that it is in the emotional domain of the mind that the energy hypothesis is operative. Aesthetic constructions are, thus, connecting agents in the knowledge-energy co-evolutionary process. Some of the macroeconomic evidence concerning the relationship between free energy use and economic growth is considered and it is found that the energy hypothesis cannot be rejected in the economic domain. However, considerably more research needs to be undertaken before any firm conclusions can be drawn
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at GeV
Identified mid-rapidity particle spectra of , , and
from 200 GeV p+p and d+Au collisions are reported. A
time-of-flight detector based on multi-gap resistive plate chamber technology
is used for particle identification. The particle-species dependence of the
Cronin effect is observed to be significantly smaller than that at lower
energies. The ratio of the nuclear modification factor () between
protons and charged hadrons () in the transverse momentum
range GeV/c is measured to be
(stat)(syst) in minimum-bias collisions and shows little
centrality dependence. The yield ratio of in minimum-bias d+Au
collisions is found to be a factor of 2 lower than that in Au+Au collisions,
indicating that the Cronin effect alone is not enough to account for the
relative baryon enhancement observed in heavy ion collisions at RHIC.Comment: 6 pages, 4 figures, 1 table. We extended the pion spectra from
transverse momentum 1.8 GeV/c to 3. GeV/
Azimuthal anisotropy at RHIC: the first and fourth harmonics
We report the first observations of the first harmonic (directed flow, v_1),
and the fourth harmonic (v_4), in the azimuthal distribution of particles with
respect to the reaction plane in Au+Au collisions at the Relativistic Heavy Ion
Collider (RHIC). Both measurements were done taking advantage of the large
elliptic flow (v_2) generated at RHIC. From the correlation of v_2 with v_1 it
is determined that v_2 is positive, or {\it in-plane}. The integrated v_4 is
about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8)
harmonics upper limits on the magnitudes are reported.Comment: 6 pages with 3 figures, as accepted for Phys. Rev. Letters The data
tables are at
http://www.star.bnl.gov/central/publications/pubDetail.php?id=3
Theorems on existence and global dynamics for the Einstein equations
This article is a guide to theorems on existence and global dynamics of
solutions of the Einstein equations. It draws attention to open questions in
the field. The local-in-time Cauchy problem, which is relatively well
understood, is surveyed. Global results for solutions with various types of
symmetry are discussed. A selection of results from Newtonian theory and
special relativity that offer useful comparisons is presented. Treatments of
global results in the case of small data and results on constructing spacetimes
with prescribed singularity structure or late-time asymptotics are given. A
conjectural picture of the asymptotic behaviour of general cosmological
solutions of the Einstein equations is built up. Some miscellaneous topics
connected with the main theme are collected in a separate section.Comment: Submitted to Living Reviews in Relativity, major update of Living
Rev. Rel. 5 (2002)
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