240 research outputs found
Numerical evidence for `multi-scalar stars'
We present a class of general relativistic soliton-like solutions composed of
multiple minimally coupled, massive, real scalar fields which interact only
through the gravitational field. We describe a two-parameter family of
solutions we call ``phase-shifted boson stars'' (parameterized by central
density rho_0 and phase delta), which are obtained by solving the ordinary
differential equations associated with boson stars and then altering the phase
between the real and imaginary parts of the field. These solutions are similar
to boson stars as well as the oscillating soliton stars found by Seidel and
Suen [E. Seidel and W.M. Suen, Phys. Rev. Lett. 66, 1659 (1991)]; in
particular, long-time numerical evolutions suggest that phase-shifted boson
stars are stable. Our results indicate that scalar soliton-like solutions are
perhaps more generic than has been previously thought.Comment: Revtex. 4 pages with 4 figures. Submitted to Phys. Rev.
Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments
Magnesite forms a series of 1- to 15-m-thick beds within the approximate to2.0 Ga (Palaeoproterozoic) Tulomozerskaya Formation, NW Fennoscandian Shield, Russia. Drillcore material together with natural exposures reveal that the 680-m-thick formation is composed of a stromatolite-dolomite-'red bed' sequence formed in a complex combination of shallow-marine and non-marine, evaporitic environments. Dolomite-collapse breccia, stromatolitic and micritic dolostones and sparry allochemical dolostones are the principal rocks hosting the magnesite beds. All dolomite lithologies are marked by delta C-13 values from +7.1 parts per thousand to +11.6 parts per thousand (V-PDB) and delta O-18 ranging from 17.4 parts per thousand to 26.3 parts per thousand (V-SMOW). Magnesite occurs in different forms: finely laminated micritic; stromatolitic magnesite; and structureless micritic, crystalline and coarsely crystalline magnesite. All varieties exhibit anomalously high delta C-13 values ranging from +9.0 parts per thousand to +11.6 parts per thousand and delta O-18 values of 20.0-25.7 parts per thousand. Laminated and structureless micritic magnesite forms as a secondary phase replacing dolomite during early diagenesis, and replaced dolomite before the major phase of burial. Crystalline and coarsely crystalline magnesite replacing micritic magnesite formed late in the diagenetic/metamorphic history. Magnesite apparently precipitated from sea water-derived brine, diluted by meteoric fluids. Magnesitization was accomplished under evaporitic conditions (sabkha to playa lake environment) proposed to be similar to the Coorong or Lake Walyungup coastal playa magnesite. Magnesite and host dolostones formed in evaporative and partly restricted environments; consequently, extremely high delta C-13 values reflect a combined contribution from both global and local carbon reservoirs. A C- 13-rich global carbon reservoir (delta C-13 at around +5 parts per thousand) is related to the perturbation of the carbon cycle at 2.0 Ga, whereas the local enhancement in C-13 (up to +12 parts per thousand) is associated with evaporative and restricted environments with high bioproductivity
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Dome growth, collapse, and valley fill at Soufrière Hills Volcano, Montserrat, from 1995 to 2013: Contributions from satellite radar measurements of topographic change
Frequent high-resolution measurements of topography at active volcanoes can provide important information for assessing the distribution and rate of emplacement of volcanic deposits and their influence on hazard. At dome-building volcanoes, monitoring techniques such as LiDAR and photogrammetry often provide a limited view of the area affected by the eruption. Here, we show the ability of satellite radar observations to image the lava dome and pyroclastic density current deposits that resulted from 15 years of eruptive activity at Soufrière Hills Volcano, Montserrat, from 1995 to 2010. We present the first geodetic measurements of the complete subaerial deposition field on Montserrat, including the lava dome. Synthetic aperture radar observations from the Advanced Land Observation Satellite (ALOS) and TanDEM-X mission are used to map the distribution and magnitude of elevation changes. We estimate a net dense-rock equivalent volume increase of 108 ± 15M m3 of the lava dome and 300 ± 220M m3 of talus and subaerial pyroclastic density current deposits. We also show variations in deposit distribution during different phases of the eruption, with greatest on-land deposition to the south and west, from 1995 to 2005, and the thickest deposits to the west and north after 2005. We conclude by assessing the potential of using radar-derived topographic measurements as a tool for monitoring and hazard assessment during eruptions at dome-building volcanoes
On Isotropic Turbulence in the Dark Fluid Universe
As first part of this work, experimental information about the decay of
isotropic turbulence in ordinary hydrodynamics, u^2(t) proportional to
t^{-6/5}, is used as input in FRW equations in order to investigate how an
initial fraction f of turbulent kinetic energy in the cosmic fluid influences
the cosmological development in the late, quintessence/phantom, universe. First
order perturbative theory to the first order in f is employed. It turns out
that both in the Hubble factor, and in the energy density, the influence from
the turbulence fades away at late times. The divergences in these quantities
near the Big Rip behave essentially as in a non-turbulent fluid. However, for
the scale factor, the turbulence modification turns out to diverge
logarithmically. As second part of our work, we consider the full FRW equation
in which the turbulent part of the dark energy is accounted for by a separate
term. It is demonstrated that turbulence occurrence may change the future
universe evolution due to dissipation of dark energy. For instance,
phantom-dominated universe becomes asymptotically a de Sitter one in the
future, thus avoiding the Big Rip singularity.Comment: 10 pages, no figures, significant revision. Matches published versio
The averaged tensors of the relative energy-momentum and angular momentum in general relativity and some their applications
There exist at least a few different kind of averaging of the differences of
the energy-momentum and angular momentum in normal coordinates {\bf NC(P)}
which give tensorial quantities. The obtained averaged quantities are
equivalent mathematically because they differ only by constant scalar
dimensional factors. One of these averaging was used in our papers [1-8] giving
the {\it canonical superenergy and angular supermomentum tensors}.
In this paper we present another averaging of the differences of the
energy-momentum and angular momentum which gives tensorial quantities with
proper dimensions of the energy-momentum and angular momentum densities. But
these averaged relative energy-momentum and angular momentum tensors, closely
related to the canonical superenergy and angular supermomentum tensors, {\it
depend on some fundamental length }.
The averaged relative energy-momentum and angular momentum tensors of the
gravitational field obtained in the paper can be applied, like the canonical
superenergy and angular supermomentum tensors, to {\it coordinate independent}
analysis (local and in special cases also global) of this field.
We have applied the averaged relative energy-momentum tensors to analyze
vacuum gravitational energy and momentum and to analyze energy and momentum of
the Friedman (and also more general) universes. The obtained results are very
interesting, e.g., the averaged relative energy density is {\it positive
definite} for the all Friedman universes.Comment: 30 pages, minor changes referring to Kasner universe
Exact Hypersurface-Homogeneous Solutions in Cosmology and Astrophysics
A framework is introduced which explains the existence and similarities of
most exact solutions of the Einstein equations with a wide range of sources for
the class of hypersurface-homogeneous spacetimes which admit a Hamiltonian
formulation. This class includes the spatially homogeneous cosmological models
and the astrophysically interesting static spherically symmetric models as well
as the stationary cylindrically symmetric models. The framework involves
methods for finding and exploiting hidden symmetries and invariant submanifolds
of the Hamiltonian formulation of the field equations. It unifies, simplifies
and extends most known work on hypersurface-homogeneous exact solutions. It is
shown that the same framework is also relevant to gravitational theories with a
similar structure, like Brans-Dicke or higher-dimensional theories.Comment: 41 pages, REVTEX/LaTeX 2.09 file (don't use LaTeX2e !!!) Accepted for
publication in Phys. Rev.
FGFR4 regulates tumor subtype differentiation in luminal breast cancer and metastatic disease
Mechanisms driving tumor progression from less aggressive subtypes to more aggressive states represent key targets for therapy. We identified a subset of luminal A primary breast tumors that give rise to HER2-enriched (HER2E) subtype metastases, but remain clinically HER2 negative (cHER2-). By testing the unique genetic and transcriptomic features of these cases, we developed the hypothesis that FGFR4 likely participates in this subtype switching. To evaluate this, we developed 2 FGFR4 genomic signatures using a patient-derived xenograft (PDX) model treated with an FGFR4 inhibitor, which inhibited PDX growth in vivo. Bulk tumor gene expression analysis and single-cell RNA sequencing demonstrated that the inhibition of FGFR4 signaling caused molecular switching. In the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) breast cancer cohort, FGFR4-induced and FGFR4-repressed signatures each predicted overall survival. Additionally, the FGFR4-induced signature was an independent prognostic factor beyond subtype and stage. Supervised analysis of 77 primary tumors with paired metastases revealed that the FGFR4-induced signature was significantly higher in luminal/ER+ tumor metastases compared with their primaries. Finally, multivariate analysis demonstrated that the FGFR4- induced signature also predicted site-specific metastasis for lung, liver, and brain, but not for bone or lymph nodes. These data identify a link between FGFR4-regulated genes and metastasis, suggesting treatment options for FGFR4-positive patients, whose high expression is not caused by mutation or amplification
Observation of direct-photon collective flow in sqrt(s_NN)=200 GeV Au+Au collisions
The second Fourier component v_2 of the azimuthal anisotropy with respect to
the reaction plane was measured for direct photons at midrapidity and
transverse momentum (p_T) of 1--13 GeV/c in Au+Au collisions at sqr(s_NN)=200
GeV. Previous measurements of this quantity for hadrons with p_T < 6 GeV/c
indicate that the medium behaves like a nearly perfect fluid, while for p_T > 6
GeV/c a reduced anisotropy is interpreted in terms of a path-length dependence
for parton energy loss. In this measurement with the PHENIX detector at the
Relativistic Heavy Ion Collider we find that for p_T > 4 GeV/c the anisotropy
for direct photons is consistent with zero, as expected if the dominant source
of direct photons is initial hard scattering. However, in the p_T < 4 GeV/c
region dominated by thermal photons, we find a substantial direct photon v_2
comparable to that of hadrons, whereas model calculations for thermal photons
in this kinematic region significantly underpredict the observed v_2.Comment: 384 authors, 6 pages, 3 figures, and 1 table. Submitted to Phys. Rev.
Lett. v2 has minor changes to match the submission version. Plain text data
tables for the points plotted in the figures are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/info/data/ppg126_data.htm
Suppression of back-to-back hadron pairs at forward rapidity in d+Au Collisions at sqrt(s_NN)=200 GeV
Back-to-back hadron pair yields in d+Au and p+p collisions at sqrt(s_NN)=200
GeV were measured with the PHENIX detector at the Relativistic Heavy Ion
Collider. Rapidity separated hadron pairs were detected with the trigger hadron
at pseudorapidity |eta|<0.35 and the associated hadron at forward rapidity
(deuteron direction, 3.0<eta<3.8). Pairs were also detected with both hadrons
measured at forward rapidity; in this case the yield of back-to-back hadron
pairs in d+Au collisions with small impact parameters is observed to be
suppressed by a factor of 10 relative to p+p collisions. The kinematics of
these pairs is expected to probe partons in the Au nucleus with low fraction x
of the nucleon momenta, where the gluon densities rise sharply. The observed
suppression as a function of nuclear thickness, p_T, and eta points to cold
nuclear matter effects arising at high parton densities.Comment: 381 authors, 6 pages, 4 figures. Published in Phys. Rev. Lett.
(http://link.aps.org/doi/10.1103/PhysRevLett.107.172301). v3 has minor
changes to match published version
(http://www.phenix.bnl.gov/phenix/WWW/info/pp1/128/PhysRevLett.107.172301)
Plain text data tables for points plotted in figures are publicly available
at http://www.phenix.bnl.gov/phenix/WWW/info/data/ppg128_data.htm
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