405 research outputs found
Spin dynamics of a trapped spin-1 Bose Gas above the Bose-Einstein transition temperature
We study collective spin oscillations in a spin-1 Bose gas above the
Bose-Einstein transition temperature. Starting from the Heisenberg equation of
motion, we derive a kinetic equation describing the dynamics of a thermal gas
with the spin-1 degree of freedom. Applying the moment method to the kinetic
equation, we study spin-wave collective modes with dipole symmetry. The dipole
modes in the spin-1 system are found to be classified into the three type of
modes. The frequency and damping rate are obtained as functions of the peak
density. The damping rate is characterized by three relaxation times associated
with collisions.Comment: 19 pages, 5 figur
Soft branes in supersymmetry-breaking backgrounds
We revisit the analysis of effective field theories resulting from
non-supersymmetric perturbations to supersymmetric flux compactifications of
the type-IIB superstring with an eye towards those resulting from the
backreaction of a small number of anti-D3-branes. Independently of the
background, we show that the low-energy Lagrangian describing the fluctuations
of a stack of probe D3-branes exhibits soft supersymmetry breaking, despite
perturbations to marginal operators that were not fully considered in some
previous treatments. We take this as an indication that the breaking of
supersymmetry by anti-D3-branes or other sources may be spontaneous rather than
explicit. In support of this, we consider the action of an anti-D3-brane
probing an otherwise supersymmetric configuration and identify a candidate for
the corresponding goldstino.Comment: 36+5 pages. References added, minor typos correcte
Anisotropic Spin Diffusion in Trapped Boltzmann Gases
Recent experiments in a mixture of two hyperfine states of trapped Bose gases
show behavior analogous to a spin-1/2 system, including transverse spin waves
and other familiar Leggett-Rice-type effects. We have derived the kinetic
equations applicable to these systems, including the spin dependence of
interparticle interactions in the collision integral, and have solved for
spin-wave frequencies and longitudinal and transverse diffusion constants in
the Boltzmann limit. We find that, while the transverse and longitudinal
collision times for trapped Fermi gases are identical, the Bose gas shows
diffusion anisotropy. Moreover, the lack of spin isotropy in the interactions
leads to the non-conservation of transverse spin, which in turn has novel
effects on the hydrodynamic modes.Comment: 10 pages, 4 figures; submitted to PR
Metastable Vacua and the Backreacted Stenzel Geometry
We construct an M-theory background dual to the metastable state recently
discussed by Klebanov and Pufu, which corresponds to placing a stack of anti-M2
branes at the tip of a warped Stenzel space. With this purpose we analytically
solve for the linearized non-supersymmetric deformations around the warped
Stenzel space, preserving the SO(5) symmetries of the supersymmetric
background, and which interpolate between the IR and UV region. We identify the
supergravity solution which corresponds to a stack of backreacting
anti-M2 branes by fixing all the 12 integration constants in terms of
. While in the UV this solution has the desired features to describe
the conjectured metastable state of the dual (2+1)-dimensional theory, in the
IR it suffers from a singularity in the four-form flux, which we describe in
some details.Comment: 33 pages, 3 figure
Higgs Boson Mass in Low Scale Gauge Mediation Models
We consider low scale gauge mediation models with a very light gravitino
m_{3/2}~16 eV, in the light of recent experimental hints on the Higgs boson
mass. The light gravitino is very interesting since there is no gravitino
over-production problem, but it seems difficult to explain the Higgs boson mass
of ~125 GeV. This is because of the conflict between the light gravitino mass
and heavy SUSY particle masses needed for producing the relatively heavy Higgs
boson mass. We consider two possible extensions in this paper: a singlet
extension of the Higgs sector, and strongly coupled gauge mediation. We show
that there is a large parameter space, in both scenarios, where the Higgs boson
mass of ~125 GeV is explained without any conflict with such a very light
gravitino.Comment: 23 pages, 5 figure
Precision Measurement of the Newtonian Gravitational Constant Using Cold Atoms
About 300 experiments have tried to determine the value of the Newtonian
gravitational constant, G, so far, but large discrepancies in the results have
made it impossible to know its value precisely. The weakness of the
gravitational interaction and the impossibility of shielding the effects of
gravity make it very difficult to measure G while keeping systematic effects
under control. Most previous experiments performed were based on the torsion
pendulum or torsion balance scheme as in the experiment by Cavendish in 1798,
and in all cases macroscopic masses were used. Here we report the precise
determination of G using laser-cooled atoms and quantum interferometry. We
obtain the value G=6.67191(99) x 10^(-11) m^3 kg^(-1) s^(-2) with a relative
uncertainty of 150 parts per million (the combined standard uncertainty is
given in parentheses). Our value differs by 1.5 combined standard deviations
from the current recommended value of the Committee on Data for Science and
Technology. A conceptually different experiment such as ours helps to identify
the systematic errors that have proved elusive in previous experiments, thus
improving the confidence in the value of G. There is no definitive relationship
between G and the other fundamental constants, and there is no theoretical
prediction for its value, against which to test experimental results. Improving
the precision with which we know G has not only a pure metrological interest,
but is also important because of the key role that G has in theories of
gravitation, cosmology, particle physics and astrophysics and in geophysical
models.Comment: 3 figures, 1 tabl
Cascades with Adjoint Matter: Adjoint Transitions
A large class of duality cascades based on quivers arising from non-isolated
singularities enjoy adjoint transitions - a phenomenon which occurs when the
gauge coupling of a node possessing adjoint matter is driven to strong coupling
in a manner resulting in a reduction of rank in the non-Abelian part of the
gauge group and a subsequent flow to weaker coupling. We describe adjoint
transitions in a simple family of cascades based on a Z2-orbifold of the
conifold using field theory. We show that they are dual to Higgsing and produce
varying numbers of U(1) factors, moduli, and monopoles in a manner which we
calculate. This realizes a large family of cascades which proceed through
Seiberg duality and Higgsing. We briefly describe the supergravity limit of our
analysis, as well as a prescription for treating more general theories. A
special role is played by N=2 SQCD. Our results suggest that additional light
fields are typically generated when UV completing certain constructions of
spontaneous supersymmetry breaking into cascades, potentially leading to
instabilities.Comment: 29 pages, a few typos fixed, improved discussion, added figure; now
there is 1 figur
Configuring urban carbon governance: insights from Sydney, Australia
In the political geography of responses to climate change, and the governance of carbon more specifically, the urban has emerged as a strategic site. Although it is recognized that urban carbon governance occurs through diverse programs and projectsâinvolving multiple actors and working through multiple sites, mechanisms, objects, and subjectsâsurprisingly little attention has been paid to the actual processes through which these diverse elements are drawn together and held together in the exercise of governing. These processesâtermed configurationâremain underspecified. This article explores urban carbon governance interventions as relational configurations, excavating how their diverse elementsâhuman, institutional, representational, and materialâare assembled, drawn into relation, and held together in the exercise of governing. Through an analysis of two contrasting case studies of urban carbon governance interventions in Sydney, Australia, we draw out common processes of configuring and specific sets of devices and techniques that gather, align, and maintain the relations between actors and elements that constitute intervention projects. We conclude by reflecting on the implications of conceiving of governing projects as relational configurations for how we understand the nature and practice of urban carbon governance, especially by revealing the diverse modes of power at work within processes of configuring
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