1,008 research outputs found
Rare radiative exclusive B decays in soft-collinear effective theory
We consider rare radiative B decays such as B -> K^* gamma or B -> rho gamma
in soft-collinear effective theory, and show that the decay amplitudes are
factorized to all orders in alpha_s and at leading order in Lambda/m_b.By
employing two-step matching, we classify the operators for radiative B decays
in powers of a small parameter lambda(~ \sqrt{Lambda/m_b}) and obtain the
relevant operators to order lambda in SCET_I. These operators are constructed
with or without spectator quarks including the four-quark operators
contributing to annihilation and W-exchange channels. And we employ SCET_II
where the small parameter becomes of order Lambda/m_b, and evolve the operators
in order to compute the decay amplitudes for rare radiative decays in
soft-collinear effective theory. We show explictly that the contributions from
the annihilation channels and the W-exchange channels vanish at leading order
in SCET. We present the factorized result for the decay amplitudes in rare
radiative B decays at leading order in SCET, and at next-to-leading order in
alpha_s.Comment: v2: 31 pages, 11 figures. An appendix is added about the quark mass
effects on radiative B decay
Comparison of BMD changes and bone formation marker levels 3 years after bisphosphonate discontinuation: FLEX and HORIZON-PFT Extension I trials
An ASBMR task force recommends a drug holiday for certain women treated for ≥5 years with oral alendronate or ≥3 years with intravenous zoledronic acid, with reassessment 2-3 years later. It is not known whether changes in BMD or bone turnover markers differ after oral or intravenous therapy. Our goal was to compare changes in BMD and procollagen type I N propeptide, PINP, after oral or intravenous bisphosphonate use. In the Fracture Intervention Trial Long-term Extension (FLEX), women who received a mean 5 years of alendronate were randomized to placebo or continued treatment. In the Health Outcomes and Reduced Incidence with Zoledronic acid Once Yearly-Pivotal Fracture Trial Extension I (HORIZON-PFT E1), women who received 3 years of zoledronic acid were randomized to placebo or continued treatment. We examined the proportion of participants with BMD loss or PINP gain ≥least significant change (LSC), and those whose values exceeded a threshold (T score ≤-2.5 or PINP ≥36.0 ng/mL, a premenopausal median value). After 3 years of placebo, the FLEX group had greater mean total hip BMD decreases (-2.3% versus -1.2% in the HORIZON-PFT E1 group, p < 0.01), and greater rises in PINP (+11.6 ng/mL versus +6.7 ng/mL, p < 0.01). There was a greater proportion of individuals in FLEX with total hip BMD loss and PINP increases that exceeded LSC, and PINP values ≥36.0 ng/mL. In contrast, there were small changes in the proportion of women with femoral neck T scores ≤-2.5 in both groups. In conclusion, 3 years after bisphosphonate discontinuation, a considerable proportion of former alendronate and zoledronic acid users had meaningful declines in total hip BMD and elevations in PINP. Despite a longer treatment course, alendronate may have a more rapid offset of drug effect than zoledronic acid
Soft, collinear and non-relativistic modes in radiative decays of very heavy quarkonium
We analyze the end-point region of the photon spectrum in semi-inclusive
radiative decays of very heavy quarkonium (m alpha_s^2 >> Lambda_QCD). We
discuss the interplay of the scales arising in the Soft-Collinear Effective
Theory, m, m(1-z)^{1/2} and m(1-z) for z close to 1, with the scales of heavy
quarkonium systems in the weak coupling regime, m, m alpha_s and m alpha_s^2.
For 1-z \sim alpha_s^2 only collinear and (ultra)soft modes are seen to be
relevant, but the recently discovered soft-collinear modes show up for 1-z <<
alpha_s^2. The S- and P-wave octet shape functions are calculated. When they
are included in the analysis of the photon spectrum of the Upsilon (1S) system,
the agreement with data in the end-point region becomes excellent. The NRQCD
matrix elements and
are also obtained.Comment: Revtex, 11 pages, 6 figures. Minor improvements and references added.
Journal versio
The COVID rehabilitation paradox: why we need to protect and develop geriatric rehabilitation services in the face of the pandemic. Comment
Older multi-morbid persons often fall seriously ill due to COVID-19. To be able to participate in a social life again, they often need special rehabilitation measures. Geriatric rehabilitation is a multi-professional service geared to these needs. Paradoxically, however, capacities in geriatric rehabilitation are currently being reduced despite increasing demand. The reasons are manifold and are not only due to the current situation. This article highlights the current situation leading to the COVID rehabilitation paradox and shows ways to learn from it for the future.</p
Generating vortex rings in Bose-Einstein condensates in the line-source approximation
We present a numerical method for generating vortex rings in Bose-Einstein
condensates confined in axially symmetric traps. The vortex ring is generated
using the line-source approximation for the vorticity, i.e., the rotational of
the superfluid velocity field is different from zero only on a circumference of
given radius located on a plane perpendicular to the symmetry axis and coaxial
with it. The particle density is obtained by solving a modified
Gross-Pitaevskii equation that incorporates the effect of the velocity field.
We discuss the appearance of density profiles, the vortex core structure and
the vortex nucleation energy, i.e., the energy difference between vortical and
ground-state configurations. This is used to present a qualitative description
of the vortex dynamics.Comment: Accepted for publication in Phys. Rev.
Gerbes, M5-Brane Anomalies and E_8 Gauge Theory
Abelian gerbes and twisted bundles describe the topology of the NS-NS 3-form
gauge field strength H. We review how they have been usefully applied to study
and resolve global anomalies in open string theory. Abelian 2-gerbes and
twisted nonabelian gerbes describe the topology of the 4-form field strength G
of M-theory. We show that twisted nonabelian gerbes are relevant in the study
and resolution of global anomalies of multiple coinciding M5-branes. Global
anomalies for one M5-brane have been studied by Witten and by Diaconescu, Freed
and Moore. The structure and the differential geometry of twisted nonabelian
gerbes (i.e. modules for 2-gerbes) is defined and studied. The nonabelian
2-form gauge potential living on multiple coinciding M5-branes arises as
curving (curvature) of twisted nonabelian gerbes. The nonabelian group is in
general , the central extension of the E_8 loop group. The
twist is in general necessary to cancel global anomalies due to the
nontriviality of the 11-dimensional 4-form G field strength and due to the
possible torsion present in the cycles the M5-branes wrap. Our description of
M5-branes global anomalies leads to the D4-branes one upon compactification of
M-theory to Type IIA theory.Comment: 19 page
An algebraic SU(1,1) solution for the relativistic hydrogen atom
The bound eigenfunctions and spectrum of a Dirac hydrogen atom are found
taking advantage of the Lie algebra in which the radial part of the
problem can be expressed. For defining the algebra we need to add to the
description an additional angular variable playing essentially the role of a
phase. The operators spanning the algebra are used for defining ladder
operators for the radial eigenfunctions of the relativistic hydrogen atom and
for evaluating its energy spectrum. The status of the Johnson-Lippman operator
in this algebra is also investigated.Comment: to appear in Physics Letters A (2005). We corrected a misprint in
page 7, in the paragraph baggining with "With the value of ..." the ground
state should be |\lambda, \lambda>, not |\lambda, \lambda+1
Electroweak and Flavour Structure of a Warped Extra Dimension with Custodial Protection
We present the electroweak and flavour structure of a model with a warped
extra dimension and the bulk gauge group SU(3) x SU(2)_L x SU(2)_R x P_LR x
U(1)_X. The presence of SU(2)_R implies an unbroken custodial symmetry in the
Higgs system allowing to eliminate large contributions to the T parameter,
whereas the P_LR symmetry and the enlarged fermion representations provide a
custodial symmetry for flavour diagonal and flavour changing couplings of the
SM Z boson to left-handed down-type quarks. We diagonalise analytically the
mass matrices of charged and neutral gauge bosons including the first KK modes.
We present the mass matrices for quarks including heavy KK modes and discuss
the neutral and charged currents involving light and heavy fields. We give the
corresponding complete set of Feynman rules in the unitary gauge.Comment: 74 pages, 2 figures. clarifying comments and references added,
version to be published in JHE
Shapes, contact angles, and line tensions of droplets on cylinders
Using an interface displacement model we calculate the shapes of
nanometer-size liquid droplets on homogeneous cylindrical surfaces. We
determine effective contact angles and line tensions, the latter defined as
excess free energies per unit length associated with the two contact lines at
the ends of the droplet. The dependences of these quantities on the cylinder
radius and on the volume of the droplets are analyzed.Comment: 26 pages, RevTeX, 10 Figure
Normal Cones and Thompson Metric
The aim of this paper is to study the basic properties of the Thompson metric
in the general case of a real linear space ordered by a cone . We
show that has monotonicity properties which make it compatible with the
linear structure. We also prove several convexity properties of and some
results concerning the topology of , including a brief study of the
-convergence of monotone sequences. It is shown most of the results are
true without any assumption of an Archimedean-type property for . One
considers various completeness properties and one studies the relations between
them. Since is defined in the context of a generic ordered linear space,
with no need of an underlying topological structure, one expects to express its
completeness in terms of properties of the ordering, with respect to the linear
structure. This is done in this paper and, to the best of our knowledge, this
has not been done yet. The Thompson metric and order-unit (semi)norms
are strongly related and share important properties, as both are
defined in terms of the ordered linear structure. Although and
are only topological (and not metrical) equivalent on , we
prove that the completeness is a common feature. One proves the completeness of
the Thompson metric on a sequentially complete normal cone in a locally convex
space. At the end of the paper, it is shown that, in the case of a Banach
space, the normality of the cone is also necessary for the completeness of the
Thompson metric.Comment: 36 page
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