1,887 research outputs found
pQCD vs. AdS/CFT Tested by Heavy Quark Energy Loss
We predict the charm and bottom quark nuclear modification factors using
weakly coupled pQCD and strongly coupled AdS/CFT drag methods. The
log(pT/M_Q)/pT dependence of pQCD loss and the momentum independence of drag
loss lead to different momentum dependencies for the R_{AA} predictions. This
difference is enhanced by examining a new experimental observable, the double
ratio of charm to bottom nuclear modification factors,
R^{cb}=R^c_{AA}/R^b_{AA}. At LHC the weakly coupled theory predicts R^{cb} goes
to 1; whereas the strongly coupled theory predicts R^{cb} .2 independent of pT.
At RHIC the differences are less dramatic, as the production spectra are
harder, but the drag formula is applicable to higher momenta, due to the lower
temperature.Comment: 6 pages, 4 figures. Proceedings for the International Conference on
Strangeness in Quark Matter (SQM 2007), Levoca, Slovakia, 24-29 June 200
Sensitivity of deexcitation energies of superdeformed secondary minima to the density dependence of symmetry energy with the relativistic mean-field theory
The relationship between deexcitation energies of superdeformed secondary
minima relative to ground states and the density dependence of the symmetry
energy is investigated for heavy nuclei using the relativistic mean field (RMF)
model. It is shown that the deexcitation energies of superdeformed secondary
minima are sensitive to differences in the symmetry energy that are mimicked by
the isoscalar-isovector coupling included in the model. With deliberate
investigations on a few Hg isotopes that have data of deexcitation energies, we
find that the description for the deexcitation energies can be improved due to
the softening of the symmetry energy. Further, we have investigated
deexcitation energies of odd-odd heavy nuclei that are nearly independent of
pairing correlations, and have discussed the possible extraction of the
constraint on the density dependence of the symmetry energy with the
measurement of deexcitation energies of these nuclei.Comment: 14 pages, 3 figure
A scalar field instability of rotating and charged black holes in (4+1)-dimensional Anti-de Sitter space-time
We study the stability of static as well as of rotating and charged black
holes in (4+1)-dimensional Anti-de Sitter space-time which possess spherical
horizon topology. We observe a non-linear instability related to the
condensation of a charged, tachyonic scalar field and construct "hairy" black
hole solutions of the full system of coupled Einstein, Maxwell and scalar field
equations. We observe that the limiting solution for small horizon radius is
either a hairy soliton solution or a singular solution that is not a regular
extremal solution. Within the context of the gauge/gravity duality the
condensation of the scalar field describes a holographic
conductor/superconductor phase transition on the surface of a sphere.Comment: 16 pages including 8 figures, v2: discussion on soliton solutions
extended; v3: matches version accepted for publication in JHE
Asymmetric neutrino emission due to neutrino-nucleon scatterings in supernova magnetic fields
We derive the cross section of neutrino-nucleon scatterings in supernova
magnetic fields, including weak-magnetism and recoil corrections. Since the
weak interaction violates the parity, the scattering cross section
asymmetrically depends on the directions of the neutrino momenta to the
magnetic field; the origin of pulsar kicks may be explained by the mechanism.
An asymmetric neutrino emission (a drift flux) due to neutrino-nucleon
scatterings is absent at the leading level of , where
is the nucleon magneton, is the magnetic field strength, and is
the matter temperature at a neutrinosphere. This is because at this level the
drift flux of the neutrinos are exactly canceled by that of the antineutrinos.
Hence, the relevant asymmetry in the neutrino emission is suppressed by much
smaller coefficient of , where is the nucleon mass;
detailed form of the relevant drift flux is also derived from the scattering
cross section, using a simple diffusion approximation. It appears that the
asymmetric neutrino emission is too small to induce the observed pulsar kicks.
However, we note the fact that the drift flux is proportional to the deviation
of the neutrino distribution function from the value of thermal equilibrium at
neutrinosphere. Since the deviation can be large for non-electron neutrinos, it
is expected that there occurs cancellation between the deviation and the small
suppression factor of . Using a simple parameterization,
we show that the drift flux due to neutrino-nucleon scatterings may be
comparable to the leading term due to beta processes with nucleons, which has
been estimated to give a relevant kick velocity when the magnetic field is
sufficiently strong as -- G.Comment: 19 pages, 1 figure. Accepted by Physical Review
Surprising Connections Between General Relativity and Condensed Matter
This brief review is intended to introduce gravitational physicists to recent
developments in which general relativity is being used to describe certain
aspects of condensed matter systems, e.g., superconductivity.Comment: 14 pages; based on talk given at GR1
The Heterotic Enhancon
The enhancon mechanism is studied in the heterotic string theory. We consider
the N_L=0 winding strings with momentum (NS1-W*) and the Kaluza-Klein dyons
(KK5-NS5*). The NS1-W* and KK5-NS5* systems are dualized to the D4-D0* and
D6-D2* systems, respectively, under the d=6 heterotic/IIA S-duality. The
heterotic form has a number of advantages over the type IIA form. We study
these backgrounds and obtain the enhancon radii by brane probe analysis. The
results are consistent with S-duality.Comment: 21 pages, 1 figure, LaTe
Relativistic analysis of the 208Pb(e,e'p)207Tl reaction at high momentum
The recent 208Pb(e,e'p)207Tl data from NIKHEF-K at high missing momentum
(p_m>300 MeV/c) are compared to theoretical results obtained with a fully
relativistic formalism previously applied to analyze data on the low missing
momentum (p_m < 300 MeV/c) region. The same relativistic optical potential and
mean field wave functions are used in the two p_m-regions. The spectroscopic
factors of the various shells are extracted from the analysis of the low-p_m
data and then used in the high-p_m region. In contrast to previous analyses
using a nonrelativistic mean field formalism, we do not find a substantial
deviation from the mean field predictions other than that of the spectroscopic
factors, which appear to be consistent with both low- and high-p_m data. We
find that the difference between results of relativistic and nonrelativistic
formalisms is enhanced in the p_m<0 region that will be interesting to explore
experimentally.Comment: 12 pages, LaTeX+Revtex, included 3 postscript figures. To appear in
the Physical Review C (Rapid Communications
Wavy Strings: Black or Bright?
Recent developments in string theory have brought forth a considerable
interest in time-dependent hair on extended objects. This novel new hair is
typically characterized by a wave profile along the horizon and angular
momentum quantum numbers in the transverse space. In this work, we
present an extensive treatment of such oscillating black objects, focusing on
their geometric properties. We first give a theorem of purely geometric nature,
stating that such wavy hair cannot be detected by any scalar invariant built
out of the curvature and/or matter fields. However, we show that the tidal
forces detected by an infalling observer diverge at the `horizon' of a black
string superposed with a vibration in any mode with . The same
argument applied to longitudinal () waves detects only finite tidal
forces. We also provide an example with a manifestly smooth metric, proving
that at least a certain class of these longitudinal waves have regular
horizons.Comment: 45 pages, latex, no figure
Thermal switch of oscillation frequency in belousov- zhabotinsky liquid marbles
© 2019 The Authors. External control of oscillation dynamics in the Belousov- Zhabotinsky (BZ) reaction is important for many applications including encoding computing schemes. When considering the BZ reaction, there are limited studies dealing with thermal cycling, particularly cooling, for external control. Recently, liquid marbles (LMs) have been demonstrated as a means of confining the BZ reaction in a system containing a solid-liquid interface. BZ LMs were prepared by rolling 50 ml droplets in polyethylene (PE) powder. Oscillations of electrical potential differences within the marble were recorded by inserting a pair of electrodes through the LM powder coating into the BZ solution core. Electrical potential differences of up to 100mV were observed with an average period of oscillation ca 44 s. BZ LMs were subsequently frozen to 218C to observe changes in the frequency of electrical potential oscillations. The frequency of oscillations reduced upon freezing to 11mHz cf. 23 mHz at ambient temperature. The oscillation frequency of the frozen BZ LM returned to 23 mHz upon warming to ambient temperature. Several cycles of frequency fluctuations were able to be achieved
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