6,551 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
Components of the gravitational force in the field of a gravitational wave
Gravitational waves bring about the relative motion of free test masses. The
detailed knowledge of this motion is important conceptually and practically,
because the mirrors of laser interferometric detectors of gravitational waves
are essentially free test masses. There exists an analogy between the motion of
free masses in the field of a gravitational wave and the motion of free charges
in the field of an electromagnetic wave. In particular, a gravitational wave
drives the masses in the plane of the wave-front and also, to a smaller extent,
back and forth in the direction of the wave's propagation. To describe this
motion, we introduce the notion of `electric' and `magnetic' components of the
gravitational force. This analogy is not perfect, but it reflects some
important features of the phenomenon. Using different methods, we demonstrate
the presence and importance of what we call the `magnetic' component of motion
of free masses. It contributes to the variation of distance between a pair of
particles. We explicitely derive the full response function of a 2-arm laser
interferometer to a gravitational wave of arbitrary polarization. We give a
convenient description of the response function in terms of the spin-weighted
spherical harmonics. We show that the previously ignored `magnetic' component
may provide a correction of up to 10 %, or so, to the usual `electric'
component of the response function. The `magnetic' contribution must be taken
into account in the data analysis, if the parameters of the radiating system
are not to be mis-estimated.Comment: prints to 29 pages including 9 figures, new title, additional
explanations and references in response to referee's comments, to be
published in Class. Quant. Gra
Updates of PDFs in the MSTW framework
I present results on updates on PDFs which are obtained within the general
framework which led to the MSTW2008 PDF sets. There are some theory and
procedural improvements and a variety of new data sets, including many relevant
up-to-date LHC data. A new set of PDFs is very close to being finalised, with
no significant changes expected to the preliminary PDFs shown here.Comment: 6 pages, 6 figures,Published in PoS DIS (2014
Black ring formation in particle systems
It is known that the formation of apparent horizons with non-spherical
topology is possible in higher-dimensional spacetimes. One of these is the
black ring horizon with topology where is the spacetime
dimension number. In this paper, we investigate the black ring horizon
formation in systems with -particles. We analyze two kinds of system: the
high-energy -particle system and the momentarily-static -black-hole
initial data. In the high-energy particle system, we prove that the black ring
horizon does not exist at the instant of collision for any . But there
remains a possibility that the black ring forms after the collision and this
result is not sufficient. Because calculating the metric of this system after
the collision is difficult, we consider the momentarily-static -black-hole
initial data that can be regarded as a simplified -particle model and
numerically solve the black ring horizon that surrounds all the particles. Our
results show that there is the minimum particle number that is necessary for
the black ring formation and this number depends on . Although many particle
number is required in five-dimensions, is sufficient for the black ring
formation in the cases. The black ring formation becomes easier for
larger . We provide a plausible physical interpretation of our results and
discuss the validity of Ida and Nakao's conjecture for the horizon formation in
higher-dimensions. Finally we briefly discuss the probable methods of producing
the black rings in accelerators.Comment: 26 pages, 7 figure
Classical stability and quantum instability of black-hole Cauchy horizons
For a certain region of the parameter space , the Cauchy
horizon of a (charged) black hole residing in de Sitter space is classically
stable to gravitational perturbations. This implies that, when left to its own
devices, classical theory is unable to retain full predictive power: the
evolution of physical fields beyond the Cauchy horizon is not uniquely
determined by the initial conditions. In this paper we argue that the Cauchy
horizon of a Reissner-Nordstr\"om-de Sitter black hole must always be unstable
quantum mechanically.Comment: 4 pages; uses ReVTeX; figure available upon request to
[email protected]
A nonlinear detection algorithm for periodic signals in gravitational wave detectors
We present an algorithm for the detection of periodic sources of
gravitational waves with interferometric detectors that is based on a special
symmetry of the problem: the contributions to the phase modulation of the
signal from the earth rotation are exactly equal and opposite at any two
instants of time separated by half a sidereal day; the corresponding is true
for the contributions from the earth orbital motion for half a sidereal year,
assuming a circular orbit. The addition of phases through multiplications of
the shifted time series gives a demodulated signal; specific attention is given
to the reduction of noise mixing resulting from these multiplications. We
discuss the statistics of this algorithm for all-sky searches (which include a
parameterization of the source spin-down), in particular its optimal
sensitivity as a function of required computational power. Two specific
examples of all-sky searches (broad-band and narrow-band) are explored
numerically, and their performances are compared with the stack-slide technique
(P. R. Brady, T. Creighton, Phys. Rev. D, 61, 082001).Comment: 9 pages, 3 figures, to appear in Phys. Rev.
Relationship between Hawking Radiation and Gravitational Anomalies
We show that in order to avoid a breakdown of general covariance at the
quantum level the total flux in each outgoing partial wave of a quantum field
in a black hole background must be equal to that of a (1+1)-dimensional
blackbody at the Hawking temperature.Comment: 5 pages, 1 figure; v2: typo corrected, reference added; v3: comment
added, minor editorial changes to agree with published versio
Safety and pharmacokinetics of dolutegravir in HIV-positive pregnant women: a systematic review
Background: The integrase strand transfer inhibitor dolutegravir (DTG) is being introduced into low- and middle-income countries (LMICs) as an alternative to first-line treatment with non-nucleoside reverse transcriptase inhibitors. However, DTG is not yet widely recommended for use in pregnant women. The aim of this systematic review was to analyse all available data on birth outcomes and congenital anomalies in the infants of pregnant women treated with DTG. Methods: A PubMed and Embase search was conducted using the terms "dolutegravir" or "DTG" and "pregnancy" or "pregnant" from the earliest available date on the database to 26 July 2017. Any reports involving women who were pregnant, HIV positive and taking DTG were included. The percentage of pregnant women with adverse birth outcomes or congenital anomalies in their infants after taking dolutegravir was compared with five historical control databases. Results: There were six databases included in the main analysis of birth outcomes and congenital anomalies, with a total of 1200 pregnant women. The percentage of pregnant women taking DTG with adverse birth outcomes and congenital abnormalities was similar to results from historical control studies of HIV-positive women. However, there was significant heterogeneity among the six databases - the percentage of infants with congenital anomalies ranged from 0.0% in Botswana (0/116 infants) to 13.3% in IMPAACT P1026S (2/15 infants). Conclusions: Up to 15 million people could be on treatment with DTG in LMICs within the next 5 years, of whom a substantial percentage is likely to be women of child-bearing potential. In many countries with large HIV epidemics, unplanned pregnancies are common and access to antenatal clinic facilities may be limited. Continued pharmacovigilance is essential, but it is reassuring that no clear safety signals have been detected, to date, for pregnant women treated with DTG in terms of birth outcomes or congenital anomalies
Non-spherical collapse of a two fluid star
We obtain the analogue of collapsing Vaidya-like solution to include both a
null fluid and a string fluid, with a linear equation of state (), in non-spherical (plane symmetric and cylindrically symmetric) anti-de
Sitter space-timess. It turns out that the non-spherical collapse of two fluid
in anti-de Sitter space-times, in accordance with cosmic censorship, proceed to
form black holes, i.e., on naked singularity ever forms, violating hoop
conjecture.Comment: 7 pages, RevTeX 4, minor correction
High Resolution Ionization of Ultracold Neutral Plasmas
Collective effects, such as waves and instabilities, are integral to our
understanding of most plasma phenomena. We have been able to study these in
ultracold neutral plasmas by shaping the initial density distribution through
spatial modulation of the ionizing laser intensity. We describe a relay imaging
system for the photoionization beam that allows us to create higher resolution
features and its application to extend the observation of ion acoustic waves to
shorter wavelengths. We also describe the formation of sculpted density
profiles to create fast expansion of plasma into vacuum and streaming plasmas
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