2,394 research outputs found
Thermal Upsilon(1s) and chi_b1 suppression in sqrt(s_NN)=2.76 TeV Pb-Pb collisions at the LHC
I compute the thermal suppression of the Upsilon(1s) and chi_b1 states in
sqrt(s_NN)=2.76 TeV Pb-Pb collisions. Using the suppression of each of these
states I estimate the total R_AA for the Upsilon(1s) state as a function of
centrality, rapidity, and transverse momentum. I find less suppression of the
chi_b1 state than would be traditionally assumed; however, my final results for
the total Upsilon(1s) suppression are in good agreement with recent preliminary
CMS data.Comment: 4 pages, 4 figures; v4: published versio
Grey seals (Halichoerus grypus) in the Dutch North sea: population ecology and effects of wind farms
This study was setup to gain an understanding of the possible effects of large-scale development of wind farms in Dutch waters on grey seals (Halichoerus grypus). This should be considered a first step in doing so as up until now relatively little was known about the species in Dutch waters. The study was carried out in the framework of WE@SEA a foundation aimed at acquiring knowledge in the field of offshore wind energy
Three flow regimes of viscous jet falling onto a moving surface
A stationary viscous jet falling from an oriented nozzle onto a moving
surface is studied, both theoretically and experimentally. We distinguish three
flow regimes and classify them by the convexity of the jet shape (concave,
vertical and convex). The fluid is modeled as a Newtonian fluid, and the model
for the flow includes viscous effects, inertia and gravity. By studying the
characteristics of the conservation of momentum for a dynamic jet, the boundary
conditions for each flow regime are derived, and the flow regimes are
characterized in terms of the process and material parameters. The model is
solved by a transformation into an algebraic equation. We make a comparison
between the model and experiments, and obtain qualitative agreement
Critical voltage of a mesoscopic superconductor
We study the role of the quasiparticle distribution function f on the
properties of a superconducting nanowire. We employ a numerical calculation
based upon the Usadel equation. Going beyond linear response, we find a
non-thermal distribution for f caused by an applied bias voltage. We
demonstrate that the even part of f (the energy mode f_L) drives a first order
transition from the superconducting state to the normal state irrespective of
the current
Falling of a viscous jet onto a moving surface
We analyze the stationary flow of a jet of Newtonian fluid that is drawn by
gravity onto a moving surface. The situation is modeled by a third-order ODE on
a domain of unknown length and with an additional integral condition; by
solving part of the equation explicitly we can reformulate the problem as a
first-order ODE, again with an integral constraint. We show that there are two
flow regimes, and characterize the associated regions in the three-dimensional
parameter space in terms of an easily calculable quantity. In a qualitative
sense the results from the model are found to correspond with experimental
observations.Comment: 16 pages, 11 figure
Transport Coefficients of Gluon Plasma
Transport coefficients of gluon plasma are calculated for a SU(3) pure gauge
model by lattice QCD simulations on and
lattices. Simulations are carried out at a slightly above the deconfinement
transition temperature , where a new state of matter is currently being
pursued in RHIC experiments. Our results show that the ratio of the shear
viscosity to the entropy is less than one and the bulk viscosity is consistent
with zero in the region, .Comment: 10 pages, Late
Quarkonium states in a complex-valued potential
We calculate quarkonium binding energies using a realistic complex-valued
potential for both an isotropic and anisotropic quark-gluon plasma. We
determine the disassociation temperatures of the ground and first excited
states considering both the real and imaginary parts of the binding energy. We
show that the effect of momentum-space anisotropy is smaller on the imaginary
part of the binding energy than on the real part of the binding energy. In the
case that one assumes an isotropic plasma, we find disassociation temperatures
for the J/psi, Upsilon and chi_b of 1.6 T_c, 2.8 T_c, and 1.5 T_c,
respectively. We find that a finite oblate momentum-space anisotropy increases
the disassociation temperature for all states considered and results in a
splitting of the p-wave states associated with the chi_b first excited state of
bottomonium.Comment: 23 pages, 9 figures; v4: subtraction of V_infinity corrected to only
subtract Re[V_infinity
Counterterms for Linear Divergences in Real-Time Classical Gauge Theories at High Temperature
Real-time classical SU() gauge theories at non-zero temperature contain
linear divergences. We introduce counterterms for these divergences in the
equations of motion in the continuum and on the lattice. These counterterms can
be given in terms of auxiliary fields that satisfy local equations of motion.
We present a lattice model with 6+1D auxiliary fields that for IR-sensitive
quantities yields cut-off independent results to leading order in the coupling.
Also an approximation with 5+1D auxiliary fields is discussed.Comment: 10 pages, major change
Shear Viscosity in the O(N) Model
We compute the shear viscosity in the O(N) model at first nontrivial order in
the large N expansion. The calculation is organized using the 1/N expansion of
the 2PI effective action (2PI-1/N expansion) to next-to-leading order, which
leads to an integral equation summing ladder and bubble diagrams. We also
consider the weakly coupled theory for arbitrary N, using the three-loop
expansion of the 2PI effective action. In the limit of weak coupling and
vanishing mass, we find an approximate analytical solution of the integral
equation. For general coupling and mass, the integral equation is solved
numerically using a variational approach. The shear viscosity turns out to be
close to the result obtained in the weak-coupling analysis.Comment: 37 pages, few typos corrected; to appear in JHE
- âŠ