580 research outputs found
Orbital-selective Mott transitions: Heavy fermions and beyond
Quantum phase transitions in metals are often accompanied by violations of
Fermi liquid behavior in the quantum critical regime. Particularly fascinating
are transitions beyond the Landau-Ginzburg-Wilson concept of a local order
parameter. The breakdown of the Kondo effect in heavy-fermion metals
constitutes a prime example of such a transition. Here, the strongly correlated
f electrons become localized and disappear from the Fermi surface, implying
that the transition is equivalent to an orbital-selective Mott transition, as
has been discussed for multi-band transition-metal oxides. In this article,
available theoretical descriptions for orbital-selective Mott transitions will
be reviewed, with an emphasis on conceptual aspects like the distinction
between different low-temperature phases and the structure of the global phase
diagram. Selected results for quantum critical properties will be listed as
well. Finally, a brief overview is given on experiments which have been
interpreted in terms of orbital-selective Mott physics.Comment: 29 pages, 4 figs, mini-review prepared for a special issue of JLT
Metal-insulator transition in the two-orbital Hubbard model at fractional band fillings: Self-energy functional approach
We investigate the infinite-dimensional two-orbital Hubbard model at
arbitrary band fillings. By means of the self-energy functional approach, we
discuss the stability of the metallic state in the systems with same and
different bandwidths. It is found that the Mott insulating phases are realized
at commensurate band fillings. Furthermore, it is clarified that the orbital
selective Mott phase with one orbital localized and the other itinerant is
stabilized even at fractional band fillings in the system with different
bandwidths.Comment: 7 pages, 10 figure
Dynamic regulation of canonical TGF beta signalling by endothelial transcription factor ERG protects from liver fibrogenesis
The role of the endothelium in protecting from chronic liver disease and TGFβ-mediated
fibrosis remains unclear. Here we describe how the endothelial transcription factor
ETS-related gene (ERG) promotes liver homoeostasis by controlling canonical TGFβ-SMAD
signalling, driving the SMAD1 pathway while repressing SMAD3 activity. Molecular analysis
shows that ERG binds to SMAD3, restricting its access to DNA. Ablation of ERG expression
results in endothelial-to-mesenchymal transition (EndMT) and spontaneous liver
fibrogenesis in EC-specific constitutive hemi-deficient (ErgcEC-Het) and inducible homozygous
deficient mice (ErgiEC-KO), in a SMAD3-dependent manner. Acute administration of the
TNF-α inhibitor etanercept inhibits carbon tetrachloride (CCL4)-induced fibrogenesis in an
ERG-dependent manner in mice. Decreased ERG expression also correlates with EndMT in
tissues from patients with end-stage liver fibrosis. These studies identify a pathogenic
mechanism where loss of ERG causes endothelial-dependent liver fibrogenesis via regulation
of SMAD2/3. Moreover, ERG represents a promising candidate biomarker for assessing
EndMT in liver disease
Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data
We present a measurement of neutrino oscillations via atmospheric muon
neutrino disappearance with three years of data of the completed IceCube
neutrino detector. DeepCore, a region of denser instrumentation, enables the
detection and reconstruction of atmospheric muon neutrinos between 10 GeV and
100 GeV, where a strong disappearance signal is expected. The detector volume
surrounding DeepCore is used as a veto region to suppress the atmospheric muon
background. Neutrino events are selected where the detected Cherenkov photons
of the secondary particles minimally scatter, and the neutrino energy and
arrival direction are reconstructed. Both variables are used to obtain the
neutrino oscillation parameters from the data, with the best fit given by
and
(normal mass hierarchy assumed). The
results are compatible and comparable in precision to those of dedicated
oscillation experiments.Comment: 10 pages, 7 figure
Searches for Extended and Point-like Neutrino Sources with Four Years of IceCube Data
We present results on searches for point-like sources of neutrinos using four
years of IceCube data, including the first year of data from the completed
86-string detector. The total livetime of the combined dataset is 1,373 days.
For an E spectrum the median sensitivity at 90\% C.L. is
TeVcms for energies between 1 TeV1 PeV in the northern
sky and TeVcms for energies between 100
TeV 100 PeV in the southern sky. The sensitivity has improved from both the
additional year of data and the introduction of improved reconstructions
compared to previous publications. In addition, we present the first results
from an all-sky search for extended sources of neutrinos. We update results of
searches for neutrino emission from stacked catalogs of sources, and test five
new catalogs; two of Galactic supernova remnants and three of active galactic
nuclei. In all cases, the data are compatible with the background-only
hypothesis, and upper limits on the flux of muon neutrinos are reported for the
sources considered.Comment: 36 pages, 15 figures. Submitted to the Astrophysical Journa
Search for Prompt Neutrino Emission from Gamma-Ray Bursts with IceCube
We present constraints derived from a search of four years of IceCube data
for a prompt neutrino flux from gamma-ray bursts (GRBs). A single
low-significance neutrino, compatible with the atmospheric neutrino background,
was found in coincidence with one of the 506 observed bursts. Although GRBs
have been proposed as candidate sources for ultra-high energy cosmic rays, our
limits on the neutrino flux disfavor much of the parameter space for the latest
models. We also find that no more than of the recently observed
astrophysical neutrino flux consists of prompt emission from GRBs that are
potentially observable by existing satellites.Comment: 15 pages, 3 figure
Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data
We present a measurement of neutrino oscillations via atmospheric muon
neutrino disappearance with three years of data of the completed IceCube
neutrino detector. DeepCore, a region of denser instrumentation, enables the
detection and reconstruction of atmospheric muon neutrinos between 10 GeV and
100 GeV, where a strong disappearance signal is expected. The detector volume
surrounding DeepCore is used as a veto region to suppress the atmospheric muon
background. Neutrino events are selected where the detected Cherenkov photons
of the secondary particles minimally scatter, and the neutrino energy and
arrival direction are reconstructed. Both variables are used to obtain the
neutrino oscillation parameters from the data, with the best fit given by
and
(normal mass hierarchy assumed). The
results are compatible and comparable in precision to those of dedicated
oscillation experiments.Comment: 10 pages, 7 figure
Measurement of the Atmospheric Spectrum with IceCube
We present a measurement of the atmospheric spectrum at energies
between 0.1 TeV and 100 TeV using data from the first year of the complete
IceCube detector. Atmospheric originate mainly from the decays of kaons
produced in cosmic-ray air showers. This analysis selects 1078 fully contained
events in 332 days of livetime, then identifies those consistent with particle
showers. A likelihood analysis with improved event selection extends our
previous measurement of the conventional fluxes to higher energies. The
data constrain the conventional flux to be times a
baseline prediction from a Honda's calculation, including the knee of the
cosmic-ray spectrum. A fit to the kaon contribution () to the neutrino
flux finds a kaon component that is times the baseline
value. The fitted/measured prompt neutrino flux from charmed hadron decays
strongly depends on the assumed astrophysical flux and shape. If the
astrophysical component follows a power law, the result for the prompt flux is
times a calculated flux based on the work by Enberg, Reno
and Sarcevic.Comment: PRD accepted versio
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