4,727 research outputs found
A Nuclear Physics Program at the ATLAS Experiment at the CERN Large Hadron Collider
The ATLAS collaboration has significant interest in the physics of
ultra-relativistic heavy ion collisions. We submitted a Letter of Intent to the
United States Department of Energy in March 2002. The following document is a
slightly modified version of that LOI. More details are available at:
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/SM/ionsComment: Letter of Intent submitted to the United States Department of Energy
Nuclear Physics Division in March 2002 (revised version
Urban socioeconomic inequality and biodiversity often converge, but not always: A global meta-analysis
It is through urban biodiversity that the majority of humans experience nature on a daily basis. As cities expand globally, it is increasingly important to understand how biodiversity is shaped by human decisions, institutions, and environments. In some cities, research has documented convergence between high socioeconomic status (SES) and high species diversity. Yet, other studies show that residents with low SES live amid high biodiversity or that SES and biodiversity appear unrelated. This study examines the conditions linked to varying types of relationships between SES and biodiversity. We identified and coded 84 case studies from 34 cities in which researchers assessed SES-biodiversity relationships. We used fuzzy-set Qualitative Comparative Analysis (fsQCA) to evaluate combinations of study design and city-level conditions that explain why SES-biodiversity relationships vary city to city and between plants and animals. While the majority of cases demonstrated increased biodiversity in higher SES neighborhoods, we identified circumstances in which inequality in biodiversity distribution was ameliorated or negated by disturbance, urban form, social policy, or collective human preference. Overall, our meta-analysis highlights the contributions of residential and municipal decisions in differentially promoting biodiversity along socioeconomic lines, situated within each city’s environmental and political context. Through identifying conditions under which access to biodiversity is more or less unequal, we call attention to outstanding research questions and raise prospects for better promoting equitable access to biodiversity
A model independent and rephase invariant parametrization of CP violation
The phenomenological description of the neutral B meson system is proposed in
terms of the fundamental CP-violating observables and within a rephasing
invariant formalism. This generic formalism can select the time-dependent and
time-integrated asymmetries which provide the basic tools to discriminate the
different kinds of possible CP-violating effects in dedicated experimental
B-meson facilities.Comment: 19 pages, Plain Te
Magnetic field tuning of antiferromagnetic YbPt
We present measurements of the specific heat, magnetization, magnetocaloric
effect and magnetic neutron diffraction carried out on single crystals of
antiferromagnetic YbPt, where highly localized Yb moments order at
K in zero field. The antiferromagnetic order was suppressed to
by applying a field of 1.85 T in the plane.
Magnetocaloric effect measurements show that the antiferromagnetic phase
transition is always continuous for , although a pronounced step
in the magnetization is observed at the critical field in both neutron
diffraction and magnetization measurements. These steps sharpen with decreasing
temperature, but the related divergences in the magnetic susceptibility are cut
off at the lowest temperatures, where the phase line itself becomes vertical in
the field-temperature plane. As , the antiferromagnetic
transition is increasingly influenced by a quantum critical endpoint, where
ultimately vanishes in a first order phase transition.Comment: 9 pages, 6 figure
Test of Special Relativity and Equivalence principle from K Physics
A violation of Local Lorentz Invariance (VLI) and hence the special theory of
relativity or a violation of equivalence principle (VEP) in the Kaon system
can, in principle, induce oscillations between and . We
construct a general formulation in which simultaneous pairwise diagonalization
of mass, momemtum, weak or gravitational eigenstates is not assumed. %and the
maximum attainable %velocities of the velocity eigenstates are different. We
discuss this problem in a general way and point out that, as expected, the VEP
and VLI contributions are indistinguishable. We then insist on the fact that
VEP or VLI can occur even when CPT is conserved. A possible CP violation of the
superweak type induced by VEP or VLI is introduced and discussed. We show that
the general VEP mechanism (or the VLI mechanism, but not both simultaneously),
with or without conserved CPT, could be clearly tested experimentally through
the energy dependence of the mass difference and of ,
, . Constraints imposed by present experiments are
calculated.Comment: Latex, 15 pages, 1 figure, version to appear in Phys. Rev.
Scaling of magnetic fluctuations near a quantum phase transition
We use inelastic neutron scattering to measure the magnetic fluctuations in a
single crystal of the heavy fermion alloy CeCu_5.9Au_0.1 close to the
antiferromagnetic quantum critical point. The energy and temperature-dependent
spectra obey (E/T) scaling at Q near (1,0,0). The neutron data and earlier bulk
susceptibility are consistent with the form 1/X ~ f(Q)+(-iE+bT)^a, with an
anomalous exponent a=0.8. We confirm the earlier observation of quasi-low
dimensionality and show how both the magnetic fluctuations and the
thermodynamics can be understood in terms of a quantum Lifshitz point.Comment: Latex file with two postscript figure
Localized moments and the stability of antiferromagnetic order in Yb3Pt4
We present here the results of electrical resistivity {\rho}, magnetization
M, ac susceptibility \c{hi}ac', and specific heat CM measurements that have
been carried out on single crystals of Yb3Pt4 over a wide range of fields and
temperatures. The 2.4-K N\'eel temperature that is found in zero field
collapses under field to a first-order transition TN=0 at BCEP=1.85 T. In the
absence of antiferromagnetic order, the specific heat CM(T,B), the
magnetization M(T,B), and even the resistivity {\rho}(T,B) all display B/T
scaling, indicating that they are dominated by strong paramagnetic
fluctuations, where the only characteristic energy scale results from the
Zeeman splitting of an energetically isolated, Yb doublet ground state. This
paramagnetic scattering disappears with the onset of antiferromagnetic order,
revealing Fermi liquid behavior {\Delta}{\rho}=AT2 that persists up to the
antiferromagnetic phase line TN(B), but not beyond. The first-order character
of TN=0 and the ubiquity of the paramagnetic fluctuations imply that
non-Fermi-liquid behaviors are absent in Yb3Pt4. In contrast to heavy fermions
such as YbRh2Si2, Yb3Pt4 represents an extremely simple regime of f-electron
behavior where the Yb moments and conduction electrons are almost decoupled,
and where Kondo physics plays little role.Comment: 10 pages,12 figure
Minimal speed of fronts of reaction-convection-diffusion equations
We study the minimal speed of propagating fronts of convection reaction
diffusion equations of the form for
positive reaction terms with . The function is continuous
and vanishes at . A variational principle for the minimal speed of the
waves is constructed from which upper and lower bounds are obtained. This
permits the a priori assesment of the effect of the convective term on the
minimal speed of the traveling fronts. If the convective term is not strong
enough, it produces no effect on the minimal speed of the fronts. We show that
if , then the minimal speed is given by
the linear value , and the convective term has no effect on the
minimal speed. The results are illustrated by applying them to the exactly
solvable case . Results are also given for
the density dependent diffusion case .Comment: revised, new results adde
- …