4,401 research outputs found
Scalar Quarkonium Masses and Mixing with the Lightest Scalar Glueball
We evaluate the continuum limit of the valence (quenched) approximation to
the mass of the lightest scalar quarkonium state, for a range of different
quark masses, and to the mixing energy between these states and the lightest
scalar glueball. Our results support the interpretation of as
composed mainly of the lightest scalar glueball.Comment: 14 pages of Latex, 5 PostScript figure
Light Hadron Spectroscopy: Theory and Experiment
Rapporteur talk at the Lepton-Photon Conference, Rome, July 2001: reviewing
the evidence and strategies for understanding scalar mesons, glueballs and
hybrids, the gluonic Pomeron and the interplay of heavy flavours and light
hadron dynamics. Dedicated to the memory of Nathan Isgur, long-time
collaborator and friend, whose original ideas in hadron spectroscopy formed the
basis for much of the talk.Comment: to be published in "Lepton Photon 2001 Conference Proceedings" (World
Scientific Publishing), 19 pages with 6 figure
‘I Stand Like A Woman’: Empowerment and Human Rights in the Context of Community-Based Reintegration of Girl Mothers Formerly Associated With Fighting Forces and Armed Groups
This article describes a multi-year participatory action research (PAR) study with young women and girls who were formerly associated with armed groups in Sierra Leone, Liberia, and northern Uganda and had children of their own during the conflict and with young mothers considered by their community to be especially vulnerable. Following a review of the literature on empowerment and human rights, the authors use examples from the PAR study to explore how empowerment and human rights relate in the context of reintegration of the most vulnerable members of society. In this context, the realization of rights and empowerment are inextricably linked as part of an iterative process. However, empowerment has been a necessary starting point for this population to experience improvements in their ability to lead dignified lives and have their rights respected. Implications for child protection and reintegration programmes are discussed
Classical capacity of bosonic broadcast communication and a new minimum output entropy conjecture
Previous work on the classical information capacities of bosonic channels has
established the capacity of the single-user pure-loss channel, bounded the
capacity of the single-user thermal-noise channel, and bounded the capacity
region of the multiple-access channel. The latter is a multi-user scenario in
which several transmitters seek to simultaneously and independently communicate
to a single receiver. We study the capacity region of the bosonic broadcast
channel, in which a single transmitter seeks to simultaneously and
independently communicate to two different receivers. It is known that the
tightest available lower bound on the capacity of the single-user thermal-noise
channel is that channel's capacity if, as conjectured, the minimum von Neumann
entropy at the output of a bosonic channel with additive thermal noise occurs
for coherent-state inputs. Evidence in support of this minimum output entropy
conjecture has been accumulated, but a rigorous proof has not been obtained. In
this paper, we propose a new minimum output entropy conjecture that, if proved
to be correct, will establish that the capacity region of the bosonic broadcast
channel equals the inner bound achieved using a coherent-state encoding and
optimum detection. We provide some evidence that supports this new conjecture,
but again a full proof is not available.Comment: 13 pages, 7 figure
Complex Probabilities on R^N as Real Probabilities on C^N and an Application to Path Integrals
We establish a necessary and sufficient condition for averages over complex
valued weight functions on R^N to be represented as statistical averages over
real, non-negative probability weights on C^N. Using this result, we show that
many path-integrals for time-ordered expectation values of bosonic degrees of
freedom in real-valued time can be expressed as statistical averages over
ensembles of paths with complex-valued coordinates, and then speculate on
possible consequences of this result for the relation between quantum and
classical mechanics.Comment: 4 pages, 0 figure
CP-PACS Result for the Quenched Light Hadron Spectrum
The quenched hadron spectrum in the continuum obtained with the Wilson quark
action in recent simulations on the CP-PACS is presented. Results for the light
quark masses and the QCD scale parameter are reported.Comment: Talk presented by K. Kanaya at Lattice97, Edinburg
Picosecond diode-pumped 1.5 μm Er,Yb:glass lasers operating at10-100 GHz repetition rate
Stable ultrafast laser sources at multi-GHz repetition rates are important for various application areas, such as optical sampling, frequency comb metrology, or advanced high-speed return-to-zero telecom systems. We review SESAM-mode-locked Er,Yb:glass lasers operating in the 1.5μm spectral region at multi-GHz repetition rates, discussing the key improvements that have enabled increasing the repetition rate up to 100GHz. We also present further improved results with shorter pulse durations from a 100GHz Er,Yb:glass laser. With an improved SESAM design we achieved 1.1ps pulses with up to 30mW average output power. Moreover, we discuss for the first time the importance of beam quality deteriorations arising from frequency-degenerate higher order spatial modes in such laser
On the Response of an OST to a Point-like Heat Source
A new technique of superconducting cavity diagnostics has been introduced by
D. Hartrill at Cornell University, Ithaca, USA. Oscillating Superleak
Transducers (OST) detect the heat transferred from a cavity's quench point via
"Second Sound" through the superfluid He bath, needed to cool the
superconducting cavity. The observed response of an OST is a complex, but
reproducible pattern of oscillations. A small helium evaporation cryostat was
built which allows the investigation of the response of an OST in greater
detail. The distance between a point-like electrical heater and the OST can be
varied. The OST can be mounted either parallel or perpendicular to the plate,
housing the heat source. If the artificial quench-point releases an amount of
energy compatible to a real quench spot on a cavity's surface, the OST signal
starts with a negative pulse, which is usually strong enough to allow automatic
detection. Furthermore, the reflection of the Second Sound on the wall is
observed. A reflection coefficient R = 0.39 +- 0.05 of the glass wall is
measured. This excludes a strong influence of multiple reflections in the
complex OST response. Fourier analyses show three main frequencies, found in
all OST spectra. They can be interpreted as modes of an oscillating circular
membrane.Comment: 10 pages, 16 figure
QCD-like Theories at Finite Baryon and Isospin Density
We use 2-color QCD as a model to study the effects of simultaneous presence
of chemical potentials for isospin charge, , and for baryon number,
. We determine the phase diagrams for 2 and 4 flavor theories using the
method of effective chiral Lagrangians at low densities and weak coupling
perturbation theory at high densities. We determine the values of various
condensates and densities as well as the spectrum of excitations as functions
of and . A similar analysis of QCD with quarks in the adjoint
representation is also presented. Our results can be of relevance for lattice
simulations of these theories. We predict a phase of inhomogeneous condensation
(Fulde-Ferrel-Larkin-Ovchinnikov phase) in the 2 colour 2 flavor theory, while
we do not expect it the 4 flavor case or in other realizations of QCD with a
positive measure.Comment: 17 pages, 14 figure
- …