10,032 research outputs found
Umklapp scattering as the origin of -linear resistivity in the normal state of high- cuprate superconductors
The high-temperature normal state of the unconventional cuprate
superconductors has resistivity linear in temperature , which persists to
values well beyond the Mott-Ioffe-Regel upper bound. At low-temperature, within
the pseudogap phase, the resistivity is instead quadratic in , as would be
expected from Fermi liquid theory. Developing an understanding of these normal
phases of the cuprates is crucial to explain the unconventional
superconductivity. We present a simple explanation for this behavior, in terms
of umklapp scattering of electrons. This fits within the general picture
emerging from functional renormalization group calculations that spurred the
Yang-Rice-Zhang ansatz: umklapp scattering is at the heart of the behavior in
the normal phase.Comment: v1 6+1 pages, 4 figures; v2 6+2 pages, 4 figures; v3 6 + 2.5 pages, 5
figure
The Magellanic Bridge: The Nearest Purely Tidal Stellar Population
We report on observations of the stellar populations in twelve fields
spanning the region between the Magellanic Clouds, made with the Mosaic-II
camera on the 4-meter telescope at the Cerro-Tololo Inter-American Observatory.
The two main goals of the observations are to characterize the young stellar
population (which presumably formed in situ in the Bridge and therefore
represents the nearest stellar population formed from tidal debris), and to
search for an older stellar component (which would have been stripped from
either Cloud as stars, by the same tidal forces which formed the gaseous
Bridge). We determine the star-formation history of the young inter-Cloud
population, which provides a constraint on the timing of the gravitational
interaction which formed the Bridge. We do not detect an older stellar
population belonging to the Bridge in any of our fields, implying that the
material that was stripped from the Clouds to form the Magellanic Bridge was
very nearly a pure gas.Comment: 19 pages, 9 figures. Accepted to Ap
Energy Balance in the Solar Transition Region. IV. Hydrogen and Helium Mass Flows With Diffusion
In this paper we have extended our previous modeling of energy balance in the
chromosphere-corona transition region to cases with particle and mass flows.
The cases considered here are quasi-steady, and satisfy the momentum and energy
balance equations in the transition region. We include in all equations the
flow velocity terms and neglect the partial derivatives with respect to time.
We present a complete and physically consistent formulation and method for
solving the non-LTE and energy balance equations in these situations, including
both particle diffusion and flows of H and He. Our results show quantitatively
how mass flows affect the ionization and radiative losses of H and He, thereby
affecting the structure and extent of the transition region. Also, our
computations show that the H and He line profiles are greatly affected by
flows. We find that line shifts are much less important than the changes in
line intensity and central reversal due to the effects of flows. In this paper
we use fixed conditions at the base of the transition region and in the
chromosphere because our intent is to show the physical effects of flows and
not to match any particular observations. However, we note that the profiles we
compute can explain the range of observed high spectral and spatial resolution
Lyman alpha profiles from the quiet Sun. We suggest that dedicated modeling of
specific sequences of observations based on physically consistent methods like
those presented here will substantially improve our understanding of the energy
balance in the chromosphere and corona.Comment: 50 pages + 20 figures; submitted to ApJ 9/10/01; a version with
higher resolution figures is available at http://cfa-www.harvard.edu/~avrett
The finite tiling problem is undecidable in the hyperbolic plane
In this paper, we consider the finite tiling problem which was proved
undecidable in the Euclidean plane by Jarkko Kari in 1994. Here, we prove that
the same problem for the hyperbolic plane is also undecidable
Gravitational wave frequencies and energies in hypernovae
A torus develops a state of suspended accretion against a magnetic wall
around a rapidly rotating black hole formed in core-collapse hypernovae. It
hereby emits about 10% of the black hole spin-energy in gravitational radiation
from a finite number of multipole mass moments. We quantify the relation
between the frequency of quadrupole gravitational radiation and the energy
output in torus winds by , where denotes the mass of the black
hole. We propose that irradiates the remnant stellar envelope from
within. We identify with energies erg inferred from X-ray
observations on matter injecta; and the poloidal curvature in the magnetic wall
with the horizon opening angle in baryon poor outflows that power true GRB
energies of erg.Comment: To appear in AP
On the origin of exponential growth in induced earthquakes in Groningen
The Groningen gas field shows exponential growth in earthquakes event counts
around a magnitude M1 with a doubling time of 6-9 years since 2001. This
behavior is identified with dimensionless curvature in land subsidence, which
has been evolving at a constant rate over the last few decades {essentially
uncorrelated to gas production.} We demonstrate our mechanism by a tabletop
crack formation experiment. The observed skewed distribution of event
magnitudes is matched by that of maxima of event clusters with a normal
distribution. It predicts about one event \,M5 per day in 2025, pointing to
increasing stress to human living conditions.Comment: 12 pages, 7 figures, to appear in Earthquakes and Structure
Entropic force in black hole binaries and its Newtonian limits
We give an exact solution for the static force between two black holes at the
turning points in their binary motion. The results are derived by Gibbs'
principle and the Bekenstein-Hawking entropy applied to the apparent horizon
surfaces in time-symmetric initial data. New power laws are derived for the
entropy jump in mergers, while Newton's law is shown to derive from a new
adiabatic variational principle for the Hilbert action in the presence of
apparent horizon surfaces. In this approach, entropy is strictly monotonic such
that gravity is attractive for all separations including mergers, and the
Bekenstein entropy bound is satisfied also at arbitrarily large separations,
where gravity reduces to Newton's law. The latter is generalized to point
particles in the Newtonian limit by application of Gibbs' principle to
world-lines crossing light cones.Comment: Accepted for publication in Phys. Rev.
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