6,699 research outputs found
The Effect of LHC Jet Data on MSTW PDFs
We consider the effect on LHC jet cross sections on partons distribution
functions (PDFs), in particular the MSTW2008 set of PDFs. We first compare the
published inclusive jet data to the predictions using MSTW2008, finding a very
good description. We also use the parton distribution reweighting procedure to
estimate the impact of these new data on the PDFs, finding that the combined
ATLAS 2.76 TeV and 7 TeV data, and CMS 7 TeV data have some significant impact.
We then also investigate the impact of ATLAS, CMS and D0 dijet data using the
same techniques. In this case we investigate the effect of using different
scale choices for the NLO cross section calculation. We find that the dijet
data is generally not completely compatible with the corresponding inclusive
jet data, often tending to pull PDFs, particularly the gluon distribution, away
from the default values. However, the effect depends on the dijet data set used
as well as the scale choice. We also note that conclusions may be affected by
limiting the pull on the data luminosity chosen by the best fit, which is
sometimes a number of standard deviations. Finally we include the inclusive jet
data in a new PDF fit explicitly. This enables us to check the consistency of
the exact result with that obtained from the reweighting procedure. There is
generally good, but not full quantitative agreement. Hence, the conclusion
remains that MSTW2008 PDFs already fit the published jet data well, but the
central values and uncertainties are altered and improved respectively by
significant, but not dramatic extent by inclusion of these data.Comment: 63 pages, 50 figures. Final version. Some added discussion and
improved figure
Deconstructing double-barred galaxies in 2D and 3D. II. Two distinct groups of inner bars
The intrinsic photometric properties of inner and outer stellar bars within
17 double-barred galaxies are thoroughly studied through a photometric analysis
consisting of: i) two-dimensional multi-component photometric decompositions,
and ii) three-dimensional statistical deprojections for measuring the
thickening of bars, thus retrieving their 3D shape. The results are compared
with previous measurements obtained with the widely used analysis of integrated
light. Large-scale bars in single- and double-barred systems show similar
sizes, and inner bars may be longer than outer bars in different galaxies. We
find two distinct groups of inner bars attending to their in-plane length and
ellipticity, resulting in a bimodal behaviour for the inner/outer bar length
ratio. Such bimodality is related neither to the properties of the host galaxy
nor the dominant bulge, and it does not show a counterpart in the dimension off
the disc plane. The group of long inner bars lays at the lower end of the outer
bar length vs. ellipticity correlation, whereas the short inner bars are out of
that relation. We suggest that this behaviour could be due to either a
different nature of the inner discs from which the inner bars are dynamically
formed, or a different assembly stage for the inner bars. This last possibility
would imply that the dynamical assembly of inner bars is a slow process taking
several Gyr to happen. We have also explored whether all large-scale bars are
prone to develop an inner bar at some stage of their lives, possibility we
cannot fully confirm or discard.Comment: 14 pages, 8 figures, 1 table. Accepted for publication in MNRA
Universal properties of the near-horizon optical geometry
We make use of the fact that the optical geometry near a static
non-degenerate Killing horizon is asymptotically hyperbolic to investigate
universal features of black hole physics. We show how the Gauss-Bonnet theorem
allows certain lensing scenarios to be ruled in or out. We find rates for the
loss of scalar, vector and fermionic `hair' as objects fall quasi- statically
towards the horizon. In the process we find the Lienard-Wiechert potential for
hyperbolic space and calculate the force between electrons mediated by
neutrinos, extending the flat space result of Feinberg and Sucher. We use the
enhanced conformal symmetry of the Schwarzschild and Reissner-Nordstrom
backgrounds to re-derive the electrostatic field due to a point charge in a
simple fashion
Locality in quantum gravity and string theory
Breakdown of local physics in string theory at distances longer than the
string scale is investigated. Such nonlocality would be expected to be visible
in ultrahigh-energy scattering. The results of various approaches to such
scattering are collected and examined. No evidence is found for non-locality
from strings whose length grows linearly with the energy. However, local
quantum field theory does apparently fail at scales determined by gravitational
physics, particularly strong gravitational dynamics. This amplifies locality
bound arguments that such failure of locality is a fundamental aspect of
physics. This kind of nonlocality could be a central element of a possible
loophole in the argument for information loss in black holes.Comment: 26 pages, 3 figures, harvmac. v2: minor changes to bring into accord
with revised paper hep-th/060519
A stochastic template placement algorithm for gravitational wave data analysis
This paper presents an algorithm for constructing matched-filter template
banks in an arbitrary parameter space. The method places templates at random,
then removes those which are "too close" together. The properties and
optimality of stochastic template banks generated in this manner are
investigated for some simple models. The effectiveness of these template banks
for gravitational wave searches for binary inspiral waveforms is also examined.
The properties of a stochastic template bank are then compared to the
deterministically placed template banks that are currently used in
gravitational wave data analysis.Comment: 14 pages, 11 figure
Distortion of Schwarzschild-anti-de Sitter black holes to black strings
Motivated by the existence of black holes with various topologies in
four-dimensional spacetimes with a negative cosmological constant, we study
axisymmetric static solutions describing any large distortions of
Schwarzschild-anti-de Sitter black holes parametrized by the mass . Under
the approximation such that is much larger than the anti-de Sitter radius,
it is found that a cylindrically symmetric black string is obtained as a
special limit of distorted spherical black holes. Such a prolonged distortion
of the event horizon connecting a Schwarzschild-anti-de Sitter black hole to a
black string is allowed without violating both the usual black hole
thermodynamics and the hoop conjecture for the horizon circumference.Comment: 13 pages, accepted for publication in Physical Review
Minimum Length from Quantum Mechanics and Classical General Relativity
We derive fundamental limits on measurements of position, arising from
quantum mechanics and classical general relativity. First, we show that any
primitive probe or target used in an experiment must be larger than the Planck
length, . This suggests a Planck-size {\it minimum ball} of uncertainty in
any measurement. Next, we study interferometers (such as LIGO) whose precision
is much finer than the size of any individual components and hence are not
obviously limited by the minimum ball. Nevertheless, we deduce a fundamental
limit on their accuracy of order . Our results imply a {\it device
independent} limit on possible position measurements.Comment: 8 pages, latex, to appear in the Physical Review Letter
Relativistic Radiative Transfer for Spherical Flows
We present a new complete set of Lagrangian relativistic hydrodynamical
equations describing the transfer of energy and momentum between a standard
fluid and a radiation fluid in a general non-stationary spherical flow. The new
set of equations has been derived for a particular application to the study of
the cosmological Quark--Hadron transition but can also be used in other
contexts.Comment: 28 pages, 9 postscript figs, Plain Te
Quantifying hiss-driven energetic electron precipitation: A detailed conjunction event analysis
Abstract We analyze a conjunction event between the Van Allen Probes and the low-altitude Polar Orbiting Environmental Satellite (POES) to quantify hiss-driven energetic electron precipitation. A physics-based technique based on quasi-linear diffusion theory is used to estimate the ratio of precipitated and trapped electron fluxes (R), which could be measured by the two-directional POES particle detectors, using wave and plasma parameters observed by the Van Allen Probes. The remarkable agreement between modeling and observations suggests that this technique is applicable for quantifying hiss-driven electron scattering near the bounce loss cone. More importantly, R in the 100-300 keV energy channel measured by multiple POES satellites over a broad L magnetic local time region can potentially provide the spatiotemporal evolution of global hiss wave intensity, which is essential in evaluating radiation belt electron dynamics, but cannot be obtained by in situ equatorial satellites alone. Key Points Measured and calculated hiss Bw from POES electron measurements agree well Electron ratio measured by POES is able to estimate hiss wave intensity This technique can be used to provide global hiss wave distributio
What is the maximum rate at which entropy of a string can increase?
According to Susskind, a string falling toward a black hole spreads
exponentially over the stretched horizon due to repulsive interactions of the
string bits. In this paper such a string is modeled as a self-avoiding walk and
the string entropy is found. It is shown that the rate at which
information/entropy contained in the string spreads is the maximum rate allowed
by quantum theory. The maximum rate at which the black hole entropy can
increase when a string falls into a black hole is also discussed.Comment: 11 pages, no figures; formulas (18), (20) are corrected (the quantum
constant is added), a point concerning a relation between the Hawking and
Hagedorn temperatures is corrected, conclusions unchanged; accepted by
Physical Review D for publicatio
- …