1,048 research outputs found
Parton showers as sources of energy-momentum deposition in the QGP and their implication for shockwave formation at RHIC and at the LHC
We derive the distribution of energy and momentum transmitted from a primary
fast parton and its medium-induced bremsstrahlung gluons to a thermalized
quark-gluon plasma. Our calculation takes into account the important and thus
far neglected effects of quantum interference between the resulting color
currents. We use our result to obtain the rate at which energy is absorbed by
the medium as a function of time and find that the rate is modified by the
quantum interference between the primary parton and secondary gluons. This
Landau-Pomeranchuk-Migdal type interference persists for time scales relevant
to heavy ion phenomenology. We further couple the newly derived source of
energy and momentum deposition to linearized hydrodynamics to obtain the bulk
medium response to realistic parton propagation and splitting in the
quark-gluon plasma. We find that because of the characteristic large angle
in-medium gluon emission and the multiple sources of energy deposition in a
parton shower, formation of well defined Mach cones by energetic jets in heavy
ion reactions is not likely.Comment: 8 pages, 4 figure
Meson Production in Proton-Proton Collisions in the Naive Non-Abelianization Approximation and the Role of Infrared Renormalons
We calculate the "naive non-abelianization" (NNA) contributions of the
higher-twist Feynman diagrams to the large- inclusive pion production
cross section in proton-proton collisions in the case of the running coupling
and frozen coupling approaches. We compare the resummed "naive
non-abelianization" higher-twist cross sections with the ones obtained in the
framework of the frozen coupling approach and leading-twist cross section. The
structure of infrared renormalon singularities of the higher twist subprocess
cross section and it's resummed expression are found. We discuss the
phenomenological consequences of possible higher-twist contributions to the
pion production in proton-proton collisions in within NNA.Comment: 17 pages, 9 figure
Narrative coherence in multiple forensic interviews with child witnesses alleging physical and sexual abuse
This study investigated the narrative coherence of children's accounts elicited in multiple forensic interviews. Transcriptions of 56 police interviews with 28 children aged 3–14 years alleging physical and sexual abuse were coded for markers of completeness, consistency and connectedness. We found that multiple interviews increased the completeness of children's testimony, containing on average almost twice as much new information as single interviews, including crucial location, time and abuse‐related details. When both contradictions within the same interview and across interviews were considered, contradictions were not more frequent in multiple interviews. The frequency of linguistic markers of connectedness remained stable across interviews. Multiple interviews increase the narrative coherence of children's testimony through increasing their completeness without necessarily introducing contradictions or decreasing causal‐temporal connections between details. However, as ‘ground truth’ is not known in field studies, further investigation of the relationship between the narrative coherence and accuracy of testimonies is required
Statistical Analysis of Small Ellerman Bomb Events
The properties of Ellerman bombs (EBs), small-scale brightenings in the
H-alpha line wings, have proved difficult to establish due to their size being
close to the spatial resolution of even the most advanced telescopes. Here, we
aim to infer the size and lifetime of EBs using high-resolution data of an
emerging active region collected using the Interferometric BIdimensional
Spectrometer (IBIS) and Rapid Oscillations of the Solar Atmosphere (ROSA)
instruments as well as the Helioseismic and Magnetic Imager (HMI) onboard the
Solar Dynamics Observatory (SDO). We develop an algorithm to track EBs through
their evolution, finding that EBs can often be much smaller (around 0.3") and
shorter lived (less than 1 minute) than previous estimates. A correlation
between G-band magnetic bright points and EBs is also found. Combining SDO/HMI
and G-band data gives a good proxy of the polarity for the vertical magnetic
field. It is found that EBs often occur both over regions of opposite polarity
flux and strong unipolar fields, possibly hinting at magnetic reconnection as a
driver of these events.The energetics of EB events is found to follow a
power-law distribution in the range of "nano-flare" (10^{22-25} ergs).Comment: 19 pages. 7 Figure
Non-perturbative QCD amplitudes in quenched and eikonal approximations
Even though approximated, strong coupling non-perturbative QCD amplitudes
remain very difficult to obtain. In this article, in eikonal and quenched
approximations, physical insights are presented that rely on the
newly-discovered property of Effective Locality.Comment: Revised version (28 pages and 1 figure in REVTeX). Follow-up work of
Eur. Phys. J. C65, pp. 395-411 (2010), (arXiv:1204.2038 [hep-ph]), and Ann.
Phys. 327, pp. 2666-2690 (2012), (arXiv:1203.6137 [hep-ph]
The European Solar Telescope (EST)
The European Solar Telescope (EST) is being designed to optimize studies of the magnetic coupling between the lower layers of the solar atmosphere (the photosphere and chromosphere) in order to investigate the origins and evolution of the solar magnetic field and its role in driving solar activity. In order to achieve this, the thermal, dynamic and magnetic properties of the solar plasma must be probed over many scale heights and at intrinsic scales, requiring the use of multi wavelength spectroscopy and spectropolarimetry at high spatial, spectral and temporal resolution. In this paper we describe some of the over-arching science questions that EST will address and briefly outline the main features of the proposed telescope design and the associated instrumentation package
The ground state energy of a massive scalar field in the background of a semi-transparent spherical shell
We calculate the zero point energy of a massive scalar field in the
background of an infinitely thin spherical shell given by a potential of the
delta function type. We use zeta functional regularization and express the
regularized ground state energy in terms of the Jost function of the related
scattering problem. Then we find the corresponding heat kernel coefficients and
perform the renormalization, imposing the normalization condition that the
ground state energy vanishes when the mass of the quantum field becomes large.
Finally the ground state energy is calculated numerically. Corresponding plots
are given for different values of the strength of the background potential, for
both attractive and repulsive potentials.Comment: 15 pages, 5 figure
Complementarity in generic open quantum systems
We develop a unified, information theoretic interpretation of the
number-phase complementarity that is applicable both to finite-dimensional
(atomic) and infinite-dimensional (oscillator) systems, with number treated as
a discrete Hermitian observable and phase as a continuous positive operator
valued measure (POVM). The relevant uncertainty principle is obtained as a
lower bound on {\it entropy excess}, , the difference between the entropy of
one variable, typically the number, and the knowledge of its complementary
variable, typically the phase, where knowledge of a variable is defined as its
relative entropy with respect to the uniform distribution. In the case of
finite dimensional systems, a weighting of phase knowledge by a factor
() is necessary in order to make the bound tight, essentially on account
of the POVM nature of phase as defined here. Numerical and analytical evidence
suggests that tends to 1 as system dimension becomes infinite. We study
the effect of non-dissipative and dissipative noise on these complementary
variables for oscillator as well as atomic systems.Comment: 18 pages, 15 figures; accepted for publication in Modern Physics
Letters
Exact gravitational lensing and rotation curve
Based on the geodesic equation in a static spherically symmetric metric we
discuss the rotation curve and gravitational lensing. The rotation curve
determines one function in the metric without assuming Einstein's equations.
Then lensing is considered in the weak field approximation of general
relativity. From the null geodesics we derive the lensing equation and
corrections to it.Comment: 12 pages, 1 figur
Representation of the three-body Coulomb Green's function in parabolic coordinates: paths of integration
The possibility is discussed of using straight-line paths of integration in
computing the integral representation of the three-body Coulomb Green's
function. In our numerical examples two different integration contours are
considered. It is demonstrated that only one of these straight-line paths
provides that the integral representation is valid
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