36,939 research outputs found
Colliders and Brane Vector Phenomenology
Brane world oscillations manifest themselves as massive vector gauge fields.
Their coupling to the Standard Model is deduced using the method of nonlinear
realizations of the spontaneously broken higher dimensional space-time
symmetries. Brane vectors are stable and weakly interacting, and therefore
escape particle detectors unnoticed. LEP and Tevatron data on the production of
a single photon in conjunction with missing energy are used to delineate
experimentally excluded regions of brane vector parameter space. The additional
region of parameter space accessible to the LHC as well as a future lepton
linear collider is also determined by means of this process.Comment: 12 pages, 13 figure
The Akulov-Volkov Lagrangian, Symmetry Currents and Spontaneously Broken Extended Supersymmetry
A generalization of the Akulov-Volkov effective Lagrangian governing the self
interactions of the Nambu-Goldstone fermions associated with spontaneously
broken extended supersymmetry as well as their coupling to matter is presented
and scrutinized. The resulting currents associated with R-symmetry,
supersymmetry and space-time translations are constructed and seen to form a
supermultiplet structure.Comment: 17 pages, LaTeX; Title, abstract and introduction changes, references
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Quantum Many-Body Dynamics of Dark Solitons in Optical Lattices
We present a fully quantum many-body treatment of dark solitons formed by
ultracold bosonic atoms in one-dimensional optical lattices. Using
time-evolving block decimation to simulate the single-band Bose-Hubbard
Hamiltonian, we consider the quantum dynamics of density and phase engineered
dark solitons as well as the quantum evolution of mean-field dark solitons
injected into the quantum model. The former approach directly models how one
may create quantum entangled dark solitons in experiment. While we have already
presented results regarding the latter approach elsewhere [Phys. Rev. Lett.
{\bf 103}, 140403 (2009)], we expand upon those results in this work. In both
cases, quantum fluctuations cause the dark soliton to fill in and may induce an
inelasticity in soliton-soliton collisions. Comparisons are made to the
Bogoliubov theory which predicts depletion into an anomalous mode that fills in
the soliton. Our many-body treatment allows us to go beyond the Bogoliubov
approximation and calculate explicitly the dynamics of the system's natural
orbitals.Comment: 14 pages, 11 figures -- v3 has only minor changes from v2 -- this is
the print versio
Rangeland biomass estimation demonstration
Because of their sensitivity to chlorophyll density, green leaf density, and leaf water density, two hand-held radiometers which have sensor bands coinciding with thematic mapper bands 3, 4, and 5 were used to calibrate green biomass to LANDSAT spectral ratios as a step towards using portable radiometers to speed up ground data acquisition. Two field reflectance panels monitored incoming radiation concurrently with sampling. Software routines were developed and used to extract data from uncorrected tapes of MSS data provided in NASA LANDSAT universal format. A LANDSAT biomass calibration curve estimated the range biomass over a four scene area and displayed this information spatially as a product in a format of use to ranchers. The regional biomass contour map is discussed
AdS-Carroll Branes
Coset methods are used to determine the action of a co-dimension one brane
(domain wall) embedded in (d+1)-dimensional AdS space in the Carroll limit in
which the speed of light goes to zero. The action is invariant under the
non-linearly realized symmetries of the AdS-Carroll spacetime. The
Nambu-Goldstone field exhibits a static spatial distribution for the brane with
a time varying momentum density related to the brane's spatial shape as well as
the AdS-C geometry. The AdS-C vector field dual theory is obtained.Comment: 47 page
Space Trumps Time When Talking About Objects
The nature of the relationship between the concepts of space and time in the human mind is much debated. Some claim that space is primary and that it structures time (cf. Lakoff & Johnson, 1980) while others (cf. Walsh, 2003) maintain no difference in status between them. Using fully immersive virtual reality (VR), we examined the influence of object distance and time of appearance on choice of demonstratives (this and that) to refer to objects. Critically, demonstratives can be used spatially (this/that red triangle) and temporally (this/that month). Experiment 1 showed a pattern of demonstrative usage in VR that is consistent with results found in real‐world studies. Experiments 2, 3, and 4 manipulated both when and where objects appeared, providing scenarios where participants were free to use demonstratives in either a temporal or spatial sense. Although we find evidence for time of presentation affecting object mention, the experiments found that demonstrative choice was affected only by distance. These results support the view that spatial uses of demonstratives are privileged over temporal uses
Challenging Magnetic Field Dependence of the Residual Resistivity of the Heavy-Fermion Metal CeCoIn5
An explanation of paradoxical behavior of the residual resistivity rho_0 of
the heavy-fermion metal CeCoIn5 in magnetic fields and under pressure is
developed. The source of this behavior is identified as a flattening of the
single-particle spectrum, which exerts profound effects on the specific heat,
thermal expansion coefficient, and magnetic susceptibility in the normal state,
the specific heat jump at the point of superconducting phase transition, and
other properties of strongly correlated electron systems in solids. It is shown
that application of a magnetic field or pressure to a system possessing a flat
band leads to a strong suppression of rho_0. Analysis of its measured
thermodynamic and transport properties yields direct evidence for the presence
of a flat band in CeCoIn5.Comment: 5 pages, 3 figures, references added, minor corrections mad
Nonlinear realization of local symmetries of AdS space
Coset methods are used to construct the action describing the dynamics
associated with the spontaneous breaking of the local symmetries of AdS_{d+1}
space due to the embedding of an AdS_d brane. The resulting action is an
SO(2,d) invariant AdS form of the Einstein-Hilbert action, which in addition to
the AdS_d gravitational vielbein, also includes a massive vector field
localized on the brane. Its long wavelength dynamics is the same as a massive
Abelian vector field coupled to gravity in AdS_d space.Comment: 17 page
Gauging Nonlinear Supersymmetry
Coset methods are used to construct the action describing the dynamics
associated with the spontaneous breaking of the local supersymmetries. The
resulting action is an invariant form of the Einstein-Hilbert action, which in
addition to the gravitational vierbein, also includes a massive gravitino
field. Invariant interactions with matter and gauge fields are also
constructed. The effective Lagrangian describing processes involving the
emission or absorption of a single light gravitino is analyzed.Comment: 20 pages, no figure
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