302,317 research outputs found
Homogeneous Lorentzian manifolds of a semisimple group
We describe the structure of -dimensional homogeneous Lorentzian
-manifolds of a semisimple Lie group . Due to a result by N.
Kowalsky, it is sufficient to consider the case when the group acts
properly, that is the stabilizer is compact. Then any homogeneous space
with a smaller group admits an invariant
Lorentzian metric. A homogeneous manifold with a connected compact
stabilizer is called a minimal admissible manifold if it admits an
invariant Lorentzian metric, but no homogeneous -manifold with
a larger connected compact stabilizer admits such a
metric. We give a description of minimal homogeneous Lorentzian -dimensional
-manifolds of a simple (compact or noncompact) Lie group . For
, we obtain a list of all such manifolds and describe invariant
Lorentzian metrics on
Fermionic topological charge of families of lattice gauge fields
Topological charge of families of lattice gauge fields is defined
fermionically via families index theory for the overlap Dirac operator. Certain
obstructions to gauge invariance of the overlap chiral fermion determinant, as
well as the lattice analogues of certain obstructions to gauge fixings without
the Gribov problem, have natural descriptions in this context.Comment: 4p., Lattice2002(chiral) (+ one paragraph not included in the
proceedings version for length reasons
Jet Studies in STAR via Di-jet Triggered (2+1) Multi-hadron Correlations
We explore jet-medium interactions via the recently developed multi-hadron
correlation or "2+1" technique. We restrict the di-jet kinematics by selecting
a pair of approximately back-to-back high pT hadron triggers and study
associated particles. Here we present our study of di-jet systematics comparing
the measurements of associate yields and spectra in 200 GeV Au+Au and d+Au
collisions in two different scenarios. We present Sum(pT) as an estimate for
energy loss. First findings indicate little to no energy loss in the symmetric
"2+1" scenario whereas model predictions are about 2 GeV.Comment: 4 pages, 3 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
The RHIC azimuth quadrupole: "perfect liquid" or gluonic radiation?
Large elliptic flow at RHIC seems to indicate that ideal hydrodynamics
provides a good description of Au-Au collisions, at least at the maximum RHIC
energy. The medium formed has been interpreted as a nearly perfect
(low-viscosity) liquid, and connections have been made to gravitation through
string theory. Recently, claimed observations of large flow fluctuations
comparable to participant eccentricity fluctuations seem to confirm the ideal
hydro scenario. However, determination of the azimuth quadrupole with 2D
angular autocorrelations, which accurately distinguish ``flow'' (quadrupole)
from ``nonflow'' (minijets), contradicts conventional interpretations.
Centrality trends may depend only on the initial parton geometry, and methods
used to isolate flow fluctuations are sensitive instead mainly to minijet
correlations. The results presented in this paper suggest that the azimuth
quadrupole may be a manifestation of gluonic multipole radiation.Comment: 11 pages, 6 figure
Elliptic Flow arising from Ridges due to Semi-hard Scattering
Azimuthal anisotropy in heavy-ion collisions is studied by taking into
account the ridges generated by semi-hard scattering of intermediate-momentum
partons, which can be sensitive to the initial spatial configuration of the
medium in non-central collisions. In a simple treatment of the problem where
the recombination of only thermal partons is considered, analytical formulas
can be derived that yield results in accord with the data on v_2 for p_T <1-2
GeV/c. Centrality dependence is described by a geometrical factor. Ridge
phenomenology is used to determine the initial slopes of v_2 at low p_T for
both pion and proton. For higher p_T, shower partons from high-p_T jets must be
included, but they are not considered here.Comment: revised version with new title and expanded discussion, to be
published in Phys. Lett.
Event anisotropy at STAR
Collective flow reflects the dynamical evolution in high-energy heavy ion
collisions. In particular, the elliptic flow reflects early collision
dynamics.We present a systematic analysis of elliptic flow () for
identified particles measured in Au + Au and Cu + Cu collisions at
= 200 GeV. Number of quark scaling is tested in the
intermediate region and in the smaller system (Cu + Cu). The Cu + Cu
collisions results are compared with those from ideal hydrodynamic model
calculations.Comment: 4 pages, 3 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
Improving the locality of the overlap Dirac operator via approximate solutions of the Ginsparg-Wilson relation
We determine the free field hypercubic Dirac operator which is optimally
close to satisfying the Ginsparg-Wilson relation. Inserting this operator into
the overlap formula, we show that the analytic locality bound on the resulting
overlap Dirac operator is substantially stronger than in the standard case.
This improvement generally persists in gauge backgrounds when the plaquette
variables are all close to unity.Comment: 3 pages, contributed to Proceedings of Lattice2003(chiral
Environmental Justice: Where are the Fracking Sites?
This paper looks at the variables that determine the location of hydraulic fracturing wells. Using cross-sectional data on Texas counties, we test whether county income level and the percentage of the population that is minority are significant indicators of well location. This study mirrors other studies that focus on the location of undesirable land uses such as landfills. Our study finds that income level and the size of the minority population are not statistically significant indicators of hydraulic fracturing well location
Urban Land Reform Briefing Paper No 6: Explaining Urban Partnership Zones
This is one of six briefing papers prepared by Professor David Adams of the University of Glasgow to
help explain key proposals for urban land reform made in 2014 by the Scottish Governmentâs Land
Reform Review Group (LRRG) to whom he acted as an independent adviser. This paper focuses on the
LRRGâs recommendations âthat the well-established international practice of property land
readjustment or land-pooling provides another effective means of addressing fragmented or multiple
ownership of land. The Group recommends that the Scottish Government investigates the potential of
introducing an Urban Partnership Zone mechanism in Scotlandâ (see pages 126-128 of the LRRG
report)
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