5,336 research outputs found
Scaling of Entanglement close to a Quantum Phase Transitions
In this Letter we discuss the entanglement near a quantum phase transition by
analyzing the properties of the concurrence for a class of exactly solvable
models in one dimension. We find that entanglement can be classified in the
framework of scaling theory. Further, we reveal a profound difference between
classical correlations and the non-local quantum correlation, entanglement: the
correlation length diverges at the phase transition, whereas entanglement in
general remains short ranged.Comment: 4 pages, 4 figures, revtex. Stylistic changes and format modifie
Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 < z < 1.0?
We present a new study investigating whether active galactic nuclei (AGN)
beyond the local universe are preferentially fed via large-scale bars. Our
investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the
AEGIS, COSMOS, and GOODS-S surveys to create samples of face-on, disc galaxies
at 0.2 < z < 1.0. We use a novel method to robustly compare a sample of 120 AGN
host galaxies, defined to have 10^42 erg/s < L_X < 10^44 erg/s, with inactive
control galaxies matched in stellar mass, rest-frame colour, size, Sersic
index, and redshift. Using the GZH bar classifications of each sample, we
demonstrate that AGN hosts show no statistically significant enhancement in bar
fraction or average bar likelihood compared to closely-matched inactive
galaxies. In detail, we find that the AGN bar fraction cannot be enhanced above
the control bar fraction by more than a factor of two, at 99.7% confidence. We
similarly find no significant difference in the AGN fraction among barred and
non-barred galaxies. Thus we find no compelling evidence that large-scale bars
directly fuel AGN at 0.2<z<1.0. This result, coupled with previous results at
z=0, implies that moderate-luminosity AGN have not been preferentially fed by
large-scale bars since z=1. Furthermore, given the low bar fractions at z>1,
our findings suggest that large-scale bars have likely never directly been a
dominant fueling mechanism for supermassive black hole growth.Comment: 13 pages, 5 figures, 2 tables, accepted by MNRA
Evaluating the competing effects of lithology and sediment supply on the erosional dynamics of rivers crossing active faults.
Lithology and sediment supply influence the erosional dynamics of rivers crossing active faults and together these effects govern the style, timescale and means by which landscapes respond to their tectono-climatic boundary conditions. Here, for transient bedrock catchments in the Gediz Graben, Turkey, and the Gulf of Corinth, Greece, for which the timing and rate of active faulting is known, we quantify the relative importance of rock strength and sediment supply on models of fluvial incision. We determine rock type, strength and erodibility using a Schmidt hammer and structural measurements of joint density and size. We evaluate the downstream distribution of channel width and stream power and calculate the extent to which the latter scales with tectonic rates and rock strength. Sediment supply is constrained using estimates of bedrock exposure, transport capacities and erosional fluxes. For the Turkish examples, stream powers in the metamorphic rocks are four times greater than in the Neogene sediment units, indicating a four-fold difference in bedrock erodibility, K, for a two-fold variation in in Schmidt hammer hardness. In the Gulf of Corinth examples, we interpret differences in stream powers near the active faults to represent order of magnitude differences in bedrock erodibility between carbonate and sandstone/conglomerate units. We also observe that in both cases, significant along-strike variation in fault slip rate is not associated with an increase in stream power for the sedimentary rocks and we assess the extent to which this stream power deficit may also represent the effects of sediment-flux-dependent incision
Stellar populations of barred quiescent galaxies
International audienceSelecting centrally quiescent galaxies from the Sloan Digital Sky Survey (SDSS) to create high signal-to-noise ratio (greater than or similar to 100 angstrom(-1)) stacked spectra with minimal emission-line contamination, we accurately and precisely model the central stellar populations of barred and unbarred quiescent disk galaxies. By splitting our sample by redshift, we can use the fixed size of the SDSS fiber to model the stellar populations at different radii within galaxies. At 0.02 \textless z \textless 0.04, the SDSS fiber radius corresponds to approximate to 1 kpc, which is the typical half-light radii of both classical bulges and disky pseudobulges. Assuming that the SDSS fiber primarily covers the bulges at these redshifts, our analysis shows that there are no significant differences in the stellar populations, i.e., stellar age, [Fe/H], [Mg/Fe], and [N/Fe], of the bulges of barred versus unbarred quiescent disk galaxies. Modeling the stellar populations at different redshift intervals from z = 0.020 to z = 0.085 at fixed stellar masses produces an estimate of the stellar population gradients out to about half the typical effective radius of our sample, assuming null evolution over this approximate to 1 Gyr epoch. We find that there are no noticeable differences in the slopes of the azimuthally averaged gradients of barred versus unbarred quiescent disk galaxies. These results suggest that bars are not a strong influence on the chemical evolution of quiescent disk galaxies
Vascular Endothelial Growth Factor A 165 rescues steroids, inflammation and follicle arrest in High Androstenedione cows
A population of cows with excess androstenedione (A4; High A4) in follicular fluid, with follicular arrest, granulosa cell dysfunction, and a 17% reduction in calving rate was previously identified. We hypothesized that excess A4 in the ovarian microenvironment caused the follicular arrest in High A4 cows and that vascular endothelial growth factor A would rescue the High A4 phenotype. In trial 1, prior to culture, High A4 ovarian cortex (n=9) had greater numbers of early stage follicles (primordial) and fewer later-stage follicles compared to controls (n=11). Culture for 7 days did not relieve this follicular arrest; instead, High A4 ovarian cortex had increased indicators of inflammation, anti-Mullerian hormone, and A4 secretion compared to controls. In trial 2, we tested if vascular endothelial growth factor A (VEGFA) angiogenic (165) and antiangiogenic (VEGFA165b) isoforms could rescue the High A4 phenotype. High A4 (n=5) and control (n=5) ovarian cortex was cultured with (1) PBS, (2) VEGFA165 (50 ng/mL), (3) VEGFA165b (50 ng/mL), or (4) VEGFA165+VEGFA165b (50 ng/mL each) for 7 days. Follicular progression increased with VEGFA165 in High A4 cows with greater early primary, primary, and secondary follicles than controls. Similar to trial 1, High A4 ovarian cortex secreted greater concentrations of A4 and other steroids and had greater indicators of inflammation compared to controls. However, VEGFA165 rescued steroidogenesis, oxidative stress, and fibrosis. Both VEGFA isoforms reduced specific pro-inflammatory cytokines in High A4 cows to control levels. Thus, VEGFA165 may be a potential therapeutic to restore the ovarian steroidogenic microenvironment to promote folliculogenesis
Galaxy Zoo: Are bars responsible for the feeding of active galactic nuclei at 0.2<z<1.0?
We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS (All-wavelength Extended Groth strip International Survey), COSMOS (Cosmological Evolution Survey), and (Great Observatories Origins Deep Survey-South) GOODS-S surveys to create samples of face-on, disc galaxies at 0.21, our findings suggest that large-scale bars have likely never directly been a dominant fuelling mechanism for supermassive black hole growt
Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 \u3c \u3cem\u3ez\u3c/em\u3e \u3c 1.0?
We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS (All-wavelength Extended Groth strip International Survey), COSMOS (Cosmological Evolution Survey), and (Great Observatories Origins Deep Survey-South) GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 \u3c z \u3c 1.0. We use a novel method to robustly compare a sample of 120 AGN host galaxies, defined to have 1042âergâsâ1 \u3c LX \u3c 1044âergâsâ1, with inactive control galaxies matched in stellar mass, rest-frame colour, size, SĂŠrsic index, and redshift. Using the GZH bar classifications of each sample, we demonstrate that AGN hosts show no statistically significant enhancement in bar fraction or average bar likelihood compared to closely-matched inactive galaxies. In detail, we find that the AGN bar fraction cannot be enhanced above the control bar fraction by more than a factor of 2, at 99.7âperâcent confidence. We similarly find no significant difference in the AGN fraction among barred and non-barred galaxies. Thus we find no compelling evidence that large-scale bars directly fuel AGN at 0.2 \u3c z \u3c 1.0. This result, coupled with previous results at z = 0, implies that moderate-luminosity AGN have not been preferentially fed by large-scale bars since z = 1. Furthermore, given the low bar fractions at z \u3e 1, our findings suggest that large-scale bars have likely never directly been a dominant fuelling mechanism for supermassive black hole growth
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
Quantum entanglement and disentanglement of multi-atom systems
We present a review of recent research on quantum entanglement, with special
emphasis on entanglement between single atoms, processing of an encoded
entanglement and its temporary evolution. Analysis based on the density matrix
formalism are described. We give a simple description of the entangling
procedure and explore the role of the environment in creation of entanglement
and in disentanglement of atomic systems. A particular process we will focus on
is spontaneous emission, usually recognized as an irreversible loss of
information and entanglement encoded in the internal states of the system. We
illustrate some certain circumstances where this irreversible process can in
fact induce entanglement between separated systems. We also show how
spontaneous emission reveals a competition between the Bell states of a two
qubit system that leads to the recently discovered "sudden" features in the
temporal evolution of entanglement. An another problem illustrated in details
is a deterministic preparation of atoms and atomic ensembles in long-lived
stationary squeezed states and entangled cluster states. We then determine how
to trigger the evolution of the stable entanglement and also address the issue
of a steered evolution of entanglement between desired pairs of qubits that can
be achieved simply by varying the parameters of a given system.Comment: Review articl
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