583 research outputs found
First search for double-beta decay of 184Os and 192Os
A search for double-beta decay of osmium has been realized for the first time
with the help of an ultra-low background HPGe gamma detector at the underground
Gran Sasso National Laboratories of the INFN (Italy). After 2741 h of data
taking with a 173 g ultra-pure osmium sample limits on double-beta processes in
184Os have been established at the level of T_{1/2} about 10^{14}-10^{17} yr.
Possible resonant double-electron captures in 184Os were searched for with a
sensitivity T_{1/2} about 10^{16} yr. A half-life limit T_{1/2} > 5.3 10^{19}
yr was set for the double-beta decay of 192Os to the first excited level of
192Pt. The radiopurity of the osmium sample has been investigated and
radionuclides 137Cs, 185Os and 207Bi were detected in the sample, while
activities of 40K, 60Co, 226Ra and 232Th were limited at the mBq/kg level.Comment: 12 pages, 7 figures, 2 table
Search for 2\beta\ decays of 96Ru and 104Ru by ultra-low background HPGe gamma spectrometry at LNGS: final results
An experiment to search for double beta decay processes in 96Ru and 104Ru,
which are accompanied by gamma rays, has been realized in the underground Gran
Sasso National Laboratories of the I.N.F.N. (Italy). Ruthenium samples with
masses of about (0.5-0.7) kg were measured with the help of ultra-low
background high purity Ge gamma ray spectrometry. After 2162 h of data taking
the samples were deeply purified to reduce the internal contamination of 40K.
The last part of the data has been accumulated over 5479 h. New improved half
life limits on 2\beta+/\epsilon \beta+/2\epsilon\ processes in 96Ru have been
established on the level of 10^{20} yr, in particular for decays to the ground
state of 96Mo: T1/2(2\nu 2\beta+) > 1.4 10^{20} yr, T1/2(2\nu \epsilon\beta+) >
8.0 10^{19} yr and T1/2(0\nu 2K) > 1.0 10^{21} yr (all limits are at 90% C.L.).
The resonant neutrinoless double electron captures to the 2700.2 keV and 2712.7
keV excited states of 96Mo are restricted as: T1/2(0\nu KL) > 2.0 10^{20} yr
and T1/2(0\nu 2L) > 3.6 10^{20} yr, respectively. Various two neutrino and
neutrinoless 2\beta\ half lives of 96Ru have been estimated in the framework of
the QRPA approach. In addition, the T1/2 limit for 0\nu 2\beta- transitions of
104Ru to the first excited state of 104Pd has been set as > 6.5 10^{20} yr.Comment: 14 pages, 5 figures, 2 tables; version accepted for publication on
Phys. Rev.
Universal properties of thermal and electrical conductivity of gauge theory plasmas from holography
We propose that for conformal field theories admitting gravity duals, the
thermal conductivity is fixed by the central charges in a universal manner.
Though we do not have a proof as yet, we have checked our proposal against
several examples. This proposal, if correct, allows us to express electrical
conductivity in terms of thermodynamical quantities even in the presence of
chemical potential.Comment: 13 pages, appendix added, close to journal versio
Constraints on Superfluid Hydrodynamics from Equilibrium Partition Functions
Following up on recent work in the context of ordinary fluids, we study the
equilibrium partition function of a 3+1 dimensional superfluid on an arbitrary
stationary background spacetime, and with arbitrary stationary background gauge
fields, in the long wavelength expansion. We argue that this partition function
is generated by a 3 dimensional Euclidean effective action for the massless
Goldstone field. We parameterize the general form of this action at first order
in the derivative expansion. We demonstrate that the constitutive relations of
relativistic superfluid hydrodynamics are significantly constrained by the
requirement of consistency with such an effective action. At first order in the
derivative expansion we demonstrate that the resultant constraints on
constitutive relations coincide precisely with the equalities between
hydrodynamical transport coefficients recently derived from the second law of
thermodynamics.Comment: 46 page
A note on conductivity and charge diffusion in holographic flavour systems
We analyze the charge diffusion and conductivity in a Dp/Dq holographic setup
that is dual to a supersymmetric Yang-Mills theory in p+1 dimensions with N_f<<
N_c flavour degrees of freedom at finite temperature and nonvanishing U(1)
baryon number chemical potential. We provide a new derivation of the results
that generalize the membrane paradigm to the present context. We perform a
numerical analysis in the particular case of the D3/D7 flavor system. The
results obtained support the validity of the Einstein relation at finite
chemical potential.Comment: 15 pages, 3 figures, v2 with minor correction
Higher Derivative Corrections to Locally Black Brane Metrics
In this paper we generalize the construction of locally boosted black brane
space time to higher derivative gravities. We consider the Gauss-Bonnet term
(with coefficient ) as a toy example. We find the solution to the
corrected Einstein equations to first order in the boundary
derivative expansion. This allows us to find the corrections to the
boundary stress tensor in the presence of the Gauss-Bonnet term in the bulk
action. We therefore obtain the ratio of shear viscosity to entropy which
agrees with other methods of computation in the literature.Comment: 0+17 page
The shear viscosity of the non-commutative plasma
We compute the shear viscosity of the non-commutative N=4 super Yang-Mills
quantum field theory at strong coupling using the dual supergravity background.
Special interest derives from the fact that the background presents an
intrinsic anisotropy in space through the distinction of commutative and
non-commutative directions. Despite this anisotropy the analysis exhibits the
ubiquitous result \eta/s = 1/4\pi for two different shear channels. In order to
derive this result, we show that the boundary energy momentum tensor must
couple to the open string metric. As a byproduct we compute the renormalised
holographic energy momentum tensor and show that it coincides with one in the
commutative theory.Comment: 17 pages. v2: reference adde
Shear Viscosity to Entropy Density Ratio in Six Derivative Gravity
We calculate shear viscosity to entropy density ratio in presence of four
derivative (with coefficient ) and six derivative (with coefficient
) terms in bulk action. In general, there can be three possible four
derivative terms and ten possible six derivative terms in the Lagrangian. Among
them two four derivative and eight six derivative terms are ambiguous, i.e.,
these terms can be removed from the action by suitable field redefinitions.
Rest are unambiguous. According to the AdS/CFT correspondence all the
unambiguous coefficients (coefficients of unambiguous terms) can be fixed in
terms of field theory parameters. Therefore, any measurable quantities of
boundary theory, for example shear viscosity to entropy density ratio, when
calculated holographically can be expressed in terms of unambiguous
coefficients in the bulk theory (or equivalently in terms of boundary
parameters). We calculate for generic six derivative gravity and find
that apparently it depends on few ambiguous coefficients at order .
We calculate six derivative corrections to central charges and and
express in terms of these central charges and unambiguous coefficients
in the bulk theory.Comment: 29 pages, no figure, V2, results and typos correcte
The ultraviolet limit and sum rule for the shear correlator in hot Yang-Mills theory
We determine a next-to-leading order result for the correlator of the shear
stress operator in high-temperature Yang-Mills theory. The computation is
performed via an ultraviolet expansion, valid in the limit of small distances
or large momenta, and the result is used for writing operator product
expansions for the Euclidean momentum and coordinate space correlators as well
as for the Minkowskian spectral density. In addition, our results enable us to
confirm and refine a shear sum rule originally derived by Romatschke, Son and
Meyer.Comment: 16 pages, 2 figures. v2: small clarifications, one reference added,
published versio
On Charged Lifshitz Black Holes
We obtain exact solutions of charged asymptotically Lifshitz black holes in
arbitrary (d+2) dimensions, generalizing the four dimensional solution
investigated in 0908.2611[hep-th]. We find that both the conventional
Hamiltonian approach and the recently proposed method for defining mass in
non-relativistic backgrounds do not work for this specific example. Thus the
mass of the black hole can only be determined by the first law of
thermodynamics. We also obtain perturbative solutions in five-dimensional
Gauss-Bonnet gravity. The ratio of shear viscosity over entropy density and the
DC conductivity are calculated in the presence of Gauss-Bonnet corrections.Comment: 24 pages, no figures, to appear in JHE
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