4,512 research outputs found
Properties of vector mesons at finite temperature -effective lagrangian approach-
The properties of -mesons at finite temperature () are examined with
an effective chiral lagrangian in which vector and axial-vector mesons are
included as massive Yang-Mills fields of the chiral symmetry. It is shown that,
at order, the effective mass is not changed but only the mixing effect in
vector and axial-vector correlator appears.Comment: 13 pages (REVTeX), two figures
Statistics of Two-point Correlation and Network Topology for Lyman Alpha Emitters at
We investigate the spatial distribution of Lyman alpha emitting galaxies
(LAEs) at , selected from the NOAO Deep Wide-Field Survey
(NDWFS), using two-point statistics and topological diagnostics adopted from
network science. We measure the clustering length, Mpc,
and the bias, . Fitting the clustering with halo
occupation distribution (HOD) models results in two disparate possibilities:
(1) where the fraction of central galaxies is 1% in halos of mass
; and (2) where the fraction is 20%. We refer to
these two scenarios as the `Dusty Core Scenario' for Model#1 since most of
central galaxies in massive halos are dead in Ly emission, and the
`Pristine Core Scenario' for Model#2 since the central galaxies are bright in
Ly emission. Traditional two-point statistics cannot distinguish
between these disparate models given the current data sets. To overcome this
degeneracy, we generate mock catalogs for each HOD model using a high
resolution -body simulation and adopt a network statistics approach, which
provides excellent topological diagnostics for galaxy point distributions. We
find three topological anomalies from the spatial distribution of observed
LAEs, which are not reproduced by the HOD mocks. We find that Model#2 matches
better all network statistics than Model#1, suggesting that the central
galaxies in halos at need to be
less dusty to be bright as LAEs, potentially implying some replenishing
channels of pristine gas such as the cold mode accretion.Comment: 23 pages, 18 figures, accepted by MNRA
Is Context-aware Reasoning = Case-based Reasoning?
The purpose of this paper is to explore the similarities and differences and then argue for the potential synergies between two methodologies, namely Context-aware Reasoning and Case-based Reasoning, that are amongst the tools which can be used for intelligent environment (IE) system development. Through a case study supported by a review of the literature, we argue that context awareness and case based reasoning are not equal and are complementary methodologies to solve a domain specific problem, rather, the IE development paradigm must build a cooperation between these two approaches to overcome the individual drawbacks and to maximise the success of the IE systems
QCD sum rule analysis for light vector and axial-vector mesons in vacuum and nuclear matter
Extending previous work we study the constraints of QCD sum rules on mass and
width of light vector and axial-vector mesons in vacuum and in a medium with
finite nuclear density. For the latter case especially the effect of nuclear
pions leading to vector-axial-vector mixing is included in the analysis.Comment: RevTeX, 32 pages, 10 eps figure
Clustering of star-forming galaxies detected in mid-infrared with the Spitzer wide-area survey
We discuss the clustering properties of galaxies with signs of ongoing star
formation detected by the Spitzer Space Telescope at 24mum band in the SWIRE
Lockman Hole field. The sample of mid-IR-selected galaxies includes ~20,000
objects detected above a flux threshold of S24mum=310muJy. We adopt
optical/near-IR color selection criteria to split the sample into the
lower-redshift and higher-redshift galaxy populations. We measure the angular
correlation function on scales of theta=0.01-3.5 deg, from which, using the
Limber inversion along with the redshift distribution established for similarly
selected source populations in the GOODS fields (Rodighiero et al. 2010), we
obtain comoving correlation lengths of r0=4.98+-0.28 h^-1 Mpc and r0
=8.04+-0.69 h^-1 Mpc for the low-z (=0.7) and high-z (=1.7) subsamples,
respectively. Comparing these measurements with the correlation functions of
dark matter halos identified in the Bolshoi cosmological simulation (Klypin et
al. 2011}, we find that the high-redshift objects reside in progressively more
massive halos reaching Mtot>3e12 h^-1 Msun, compared to Mtot>7e11 h^-1 Msun for
the low-redshift population. Approximate estimates of the IR luminosities based
on the catalogs of 24mum sources in the GOODS fields show that our high-z
subsample represents a population of "distant ULIRGs" with LIR>10^12Lsun, while
the low-z subsample mainly consists of "LIRGs", LIR~10^11Lsun. The comparison
of number density of the 24mum selected galaxies and of dark matter halos with
derived minimum mass Mtot shows that only 20% of such halos may host
star-forming galaxies.Comment: 15 pages, 12 figure
Geometric and Electronic Structures of the NiI and Methyl−NiIII Intermediates of Methyl-Coenzyme M Reductase†
ABSTRACT: Methyl-coenzyme M reductase (MCR) catalyzes the terminal step in the formation of biological methane from methyl-coenzyme M (Me-SCoM) and coenzyme B (CoBSH). The active site in MCR contains a Ni-F430 cofactor, which can exist in different oxidation states. The catalytic mechanism of methane formation has remained elusive despite intense spectroscopic and theoretical investigations. On the basis of spectroscopic and crystallographic data, the first step of the mechanism is proposed to involve a nucleophilic attack of the NiI active state (MCRred1) on Me-SCoM to form a NiIII-methyl intermediate, while computational studies indicate that the first step involves the attack of NiI on the sulfur of Me-SCoM, forming a CH3 radical and a NiII-thiolate species. In this study, a combination of Ni K-edge X-ray absorption spectroscopic (XAS) studies and density functional theory (DFT) calculations have been performed on the NiI (MCRred1), NiII (MCRred1-silent), and NiIII-methyl (MCRMe) states of MCR to elucidate the geometric and electronic structures of the different redox states. Ni K-edge EXAFS data are used to reveal a five-coordinate active site with an open upper axial coordination site in MCRred1. Ni K-pre-edge and EXAFS data and time-dependent DFT calculations unambiguously demonstrate the presence of a long Ni-C bond (∼2.04 Å) in the NiIII-methyl state of MCR. The formation and stability of this species support mechanism I, and the Ni-C bond length suggests a homolytic cleavage of the NiIII-methyl bon
Non SUSY Unification in Left-Right Models
We explore in a model independent way the possibility of achieving the non
supersymmetric gauge coupling unification within left-right symmetric models,
with the minimal particle content at the left-right mass scale which could be
as low as 1 TeV in a variety of models, and with a unification scale M in the
range GeV GeV.Comment: 18 pages, Latex file, uses epsf style, four figures. Submitted for
publication to Phys. Rev. D on Oct. 13, 199
Spitzer 70/160 μm observations of high-redshift ULIRGs and HyLIRSs in the Boötes field
We present new 70 and 160 μm observations of a sample of extremely red (R – [24] ≳ 15 mag), mid-infrared bright, high-redshift (1.7 ≾ z ≾ 2.8) galaxies. All targets detected in the far-infrared exhibit rising spectral energy distributions (SEDs) consistent with dust emission from obscured active galactic nuclei (AGNs) and/or star-forming regions in luminous IR galaxies (LIRGs). We find that the SEDs of the high-redshift sources are more similar to canonical AGN-dominated local ultraluminous IR galaxies (ULIRGs) with significant warm dust components than to typical local star-forming ULIRGs. The inferred IR (8-1000 μm) bolometric luminosities are found to be Lbol ~ 4 × 10^12 L⊙ to ~3 × 10^13 L⊙ (ULIRGs/hyper-luminous IR galaxies (HyLIRGs)), representing the first robust constraints on Lbol for this class of object
Dark Matter Candidates: A Ten-Point Test
An extraordinarily rich zoo of non-baryonic Dark Matter candidates has been
proposed over the last three decades. Here we present a 10-point test that a
new particle has to pass, in order to be considered a viable DM candidate: I.)
Does it match the appropriate relic density? II.) Is it {\it cold}? III.) Is it
neutral? IV.) Is it consistent with BBN? V.) Does it leave stellar evolution
unchanged? VI.) Is it compatible with constraints on self-interactions? VII.)
Is it consistent with {\it direct} DM searches? VIII.) Is it compatible with
gamma-ray constraints? IX.) Is it compatible with other astrophysical bounds?
X.) Can it be probed experimentally?Comment: 29 pages, 12 figure
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