2,415 research outputs found
Lattice renormalisation of O(a) improved heavy-light operators: an addendum
The analytical expressions and the numerical values of the renormalisation
constants of dimension 3 static-light currents are given at one-loop order of
perturbation theory in the framework of Heavy Quark Effective Theory and with
an improved gauge action: the static quark is described by the HYP-smeared
action and the light quark is of Wilson kind. This completes a work started few
years ago and is actually an intermediate step in the measurement of the decay
constants and by the European Twisted Mass Collaboration
[arXiv:1107.1441[hep-lat]].Comment: 5 pages, no figure
A geometric study of Wasserstein spaces: Hadamard spaces
Optimal transport enables one to construct a metric on the set of
(sufficiently small at infinity) probability measures on any (not too wild)
metric space X, called its Wasserstein space W(X). In this paper we investigate
the geometry of W(X) when X is a Hadamard space, by which we mean that has
globally non-positive sectional curvature and is locally compact. Although it
is known that -except in the case of the line- W(X) is not non-positively
curved, our results show that W(X) have large-scale properties reminiscent of
that of X. In particular we define a geodesic boundary for W(X) that enables us
to prove a non-embeddablity result: if X has the visibility property, then the
Euclidean plane does not admit any isometric embedding in W(X).Comment: This second version contains only the first part of the preceeding
one. The visibility properties of W(X) and the isometric rigidity have been
split off to other articles after a referee's commen
Archeops: an instrument for present and future cosmology
Archeops is a balloon-borne instrument dedicated to measure the cosmic
microwave background (CMB) temperature anisotropies. It has, in the millimetre
domain (from 143 to 545 GHz), a high angular resolution (about 10 arcminutes)
in order to constrain high l multipoles, as well as a large sky coverage
fraction (30%) in order to minimize the cosmic variance. It has linked, before
WMAP, Cobe large angular scales to the first acoustic peak region. From its
results, inflation motivated cosmologies are reinforced with a flat Universe
(Omega_tot=1 within 3%). The dark energy density and the baryonic density are
in very good agreement with other independent estimations based on supernovae
measurements and big bang nucleosynthesis. Important results on galactic dust
emission polarization and their implications for Planck are also addressed.Comment: 4 pages, 2 figures, to appear in Proceedings of the Multiwavelength
Cosmology Conference, June 2003, Mykonos Island, Greec
Lattice renormalisation of O(a) improved heavy-light operators
The analytical expressions and the numerical values of the renormalisation
constants of improved static-light currents are given at one-loop
order of perturbation theory in the framework of Heavy Quark Effective Theory:
the static quark is described by the HYP action and the light quark is
described either with the Clover or the Neuberger action. These factors are
relevant to extract from a lattice computation the decay constants ,
and the set of bag parameters associated with
mixing phenomenology in the Standard Model and beyond.Comment: 16 pages, 2 figures, 4 tables; few comments and references added;
version to be published in Phys Rev
Random quantum channels I: graphical calculus and the Bell state phenomenon
This paper is the first of a series where we study quantum channels from the
random matrix point of view. We develop a graphical tool that allows us to
compute the expected moments of the output of a random quantum channel. As an
application, we study variations of random matrix models introduced by Hayden
\cite{hayden}, and show that their eigenvalues converge almost surely. In
particular we obtain for some models sharp improvements on the value of the
largest eigenvalue, and this is shown in a further work to have new
applications to minimal output entropy inequalities.Comment: Several typos were correcte
Light dressed-excitons in an incoherent-electron sea: Evidence for Mollow-triplet and Autler-Townes doublet
We demonstrate that the interaction between excitons and a sea of incoherent
electrons does not preclude excitons dressing by light. We investigate the role
of exciton-electron scattering in the light dressing by measuring the dynamical
absorption spectrum of a modulation-doped CdTe quantum well, which shows a
clear evidence for significant electron scattering of the excitonic states. We
show the occurrence of dressed and correlated excitons by detecting quantum
coherent interferences through excitonic Autler-Townes doublet and ac Stark
splitting, which evolves to Mollow triplet with gain. We also evidence the
partial inhibition of the electron-exciton scattering by exciton-light
coupling
Nernst quantum oscillations in bulk semi-metals
With a widely available magnetic field of 10 T, one can attain the quantum
limit in bismuth and graphite. At zero magnetic field, these two elemental
semi-metals host a dilute liquid of carriers of both signs. When the quantum
limit is attained, all quasi-particles are confined to a few Landau tubes. Each
time a Landau tube is squeezed before definitely leaving the Fermi surface, the
Nernst response sharply peaks. In bismuth, additional Nernst peaks, unexpected
in the non-interacting picture, are resolved beyond the quantum limit. The
amplitude of these unexpected Nernst peaks is larger in the samples with the
longest electron mean-free-path.Comment: Accepted for publication in Journal of Physics: Condensed Matter's
special issue on Strongly Correlated Electron Systems(SCES
Hall plateaus at magic angles in bismuth beyond the quantum limit
We present a study of the angular dependence of the resistivity tensor up to
35 T in elemental bismuth complemented by torque magnetometry measurements in a
similar configuration. For at least two particular field orientations a few
degrees off the trigonal axis, the Hall resistivity was found to become
field-independent within experimental resolution in a finite field window
corresponding to a field which is roughly three times the frequency of quantum
oscillations. The Hall plateaus rapidly vanish as the field is tilted off
theses magic angles. We identify two distinct particularities of these specific
orientations, which may play a role in the emergence of the Hall plateaus.Comment: 5 pages, 5 figure
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