10,260 research outputs found
Dynamics of rapidly rotating Bose-Einstein condensates in a harmonic plus quartic trap
A two-dimensional rapidly rotating Bose-Einstein condensate in a harmonic
plus quartic trap is expected to have unusual vortex states that do not occur
in a pure harmonic trap. At a critical rotation speed , a central
hole appears in the condensate, and at some faster rotation speed ,
the system undergoes a transition to a giant vortex state with pure
irrotational flow. Using a time-dependent variational analysis, we study the
behavior of an annular condensate with a single concentric ring of vortices.
The transition to a giant vortex state is investigated by comparing the energy
of the two equilibrium states (the ring of vortices and the giant vortex) and
also by studying the dynamical stability of small excitation modes of the ring
of vortices.Comment: 12pages, 4figure
Lines and Boxes: Unmasking Dynamical Dark Matter through Correlations in the MeV Gamma-Ray Spectrum
Identifying signatures of dark matter at indirect-detection experiments is
generally more challenging for scenarios involving non-minimal dark sectors
such as Dynamical Dark Matter (DDM) than for scenarios involving a single dark
particle. This additional difficulty arises because the partitioning of the
total dark-matter abundance across an ensemble of different constituent
particles with different masses tends to "smear" the injection spectra of
photons and other cosmic-ray particles that are produced via dark-matter
annihilation or decay. As a result, the imprints of the dark sector on these
cosmic-ray flux spectra typically take the form of continuum features rather
than sharp peaks or lines. In this paper, however, we identify an unambiguous
signature of non-minimal dark sectors such as DDM which can overcome these
issues and potentially be observed at gamma-ray telescopes operating in the MeV
range. We discuss the specific situations in which this signature can arise,
and demonstrate that this signature can be exploited in order to significantly
enhance our ability to resolve the unique spectral features of DDM and other
non-minimal dark sectors at future gamma-ray facilities.Comment: 21 pages, LaTeX, 4 figures, 1 tabl
Boxes, Boosts, and Energy Duality: Understanding the Galactic-Center Gamma-Ray Excess through Dynamical Dark Matter
Many models currently exist which attempt to interpret the excess of gamma
rays emanating from the Galactic Center in terms of annihilating or decaying
dark matter. These models typically exhibit a variety of complicated cascade
mechanisms for photon production, leading to a non-trivial kinematics which
obscures the physics of the underlying dark sector. In this paper, by contrast,
we observe that the spectrum of the gamma-ray excess may actually exhibit an
intriguing "energy-duality" invariance under for some . As we shall discuss, such an energy
duality points back to a remarkably simple alternative kinematics which in turn
is realized naturally within the Dynamical Dark Matter framework. Observation
of this energy duality could therefore provide considerable information about
the properties of the dark sector from which the Galactic-Center gamma-ray
excess might arise, and highlights the importance of acquiring more complete
data for the Galactic-Center excess in the energy range around 1 GeV.Comment: 13 pages, LaTeX, 5 figure
Patterns of Striped order in the Classical Lattice Coulomb Gas
We obtain via Monte Carlo simulations the low temperature charge
configurations in the lattice Coulomb gas on square lattices for charge filling
ratio in the range . We find a simple regularity in the low
temperature charge configurations which consist of a suitable periodic
combination of a few basic striped patterns characterized by the existence of
partially filled diagonal channels. In general there exist two separate
transitions where the lower temperature transition () corresponds to the
freezing of charges within the partially filled channels. is found to be
sensitively dependent on through the charge number density within the channels.Comment: 4 pages, 8 figure
Electroweak Contributions to Squark Pair Production at the LHC
In this paper we compute electroweak contributions to the production of
squark pairs at hadron colliders. These include the exchange of electroweak
gauge bosons in the s-channel as well as electroweak gaugino exchange in the t-
and/or u-channel. In many cases these can interfere with the dominant QCD
contributions. As a result, we find sizable contributions to the production of
two SU(2) doublet squarks. At the LHC, they amount to 10 to 20% for typical
mSUGRA (or CMSSM) scenarios, but in more general scenarios they can vary
between -40 and +55%, depending on size and sign of the SU(2) gaugino mass. The
electroweak contribution to the total squark pair production rate at the LHC is
about 3.5 times smaller.Comment: 28 pages, 9 figure
Sudden Event Monitoring of Civil Infrastructure Using Demand-Based Wireless Smart Sensors
Wireless smart sensors (WSS) have been proposed as an effective means to reduce the
high cost of wired structural health monitoring systems. However, many damage scenarios for civil
infrastructure involve sudden events, such as strong earthquakes, which can result in damage or even
failure in a matter of seconds. Wireless monitoring systems typically employ duty cycling to reduce
power consumption; hence, they will miss such events if they are in power-saving sleep mode when
the events occur. This paper develops a demand-based WSS to meet the requirements of sudden event
monitoring with minimal power budget and low response latency, without sacrificing high-fidelity
measurements or risking a loss of critical information. In the proposed WSS, a programmable
event-based switch is implemented utilizing a low-power trigger accelerometer; the switch is
integrated in a high-fidelity sensor platform. Particularly, the approach can rapidly turn on the
WSS upon the occurrence of a sudden event and seamlessly transition from low-power acceleration
measurement to high-fidelity data acquisition. The capabilities of the proposed WSS are validated
through laboratory and field experiments. The results show that the proposed approach is able
to capture the occurrence of sudden events and provide high-fidelity data for structural condition
assessment in an efficient manner
Collective resonance modes of Josephson vortices in sandwiched stack of BiSrCaCuO intrinsic Josephson junctions
We observed splitting of the low-bias vortex-flow branch in a
dense-Josephson-vortex state into multiple sub-branches in current-voltage
characteristics of intrinsic Josephson junctions (IJJs) of
BiSrCaCuO single crystals in the long-junction limit.
Each sub-branch corresponds to a plasma mode in serially coupled Josephson
junctions. Splitting into low-bias linear sub-branches with a spread in the
slopes and the inter-sub-branch mode-switching character are in good
quantitative agreement with the prediction of the weak but finite
inter-junction capacitive-coupling model incorporated with the inductive
coupling. This suggests the importance of the role of the capacitive coupling
in accurately describing the vortex dynamics in serially stacked IJJs.Comment: 4 pages, 3 figures, 1 tabl
Human CD57(+ )germinal center-T cells are the major helpers for GC-B cells and induce class switch recombination
BACKGROUND: The function of CD57(+ )CD4(+ )T cells, constituting a major subset of germinal center T (GC-Th) cells in human lymphoid tissues, has been unclear. There have been contradictory reports regarding the B cell helping function of CD57(+ )GC-Th cells in production of immunoglobulin (Ig). Furthermore, the cytokine and co-stimulation requirement for their helper activity remains largely unknown. To clarify and gain more insight into their function in helping B cells, we systematically investigated the capacity of human tonsil CD57(+ )GC-Th cells in inducing B cell Ig synthesis. RESULTS: We demonstrated that CD57(+ )GC-Th cells are highly efficient in helping B cell production of all four subsets of Ig (IgM, IgG, IgA and IgE) compared to other T-helper cells located in germinal centers or interfollicular areas. CD57(+ )GC-Th cells were particularly more efficient than other T cells in helping GC-B cells but not naïve B cells. CD57(+ )GC-Th cells induced the expression of activation-induced cytosine deaminase (AID) and class switch recombination in developing B cells. IgG1-3 and IgA1 were the major Ig isotypes induced by CD57(+ )GC-Th cells. CD40L, but not IL-4, IL-10 and IFN-γ, was critical in CD57(+ )GC-Th cell-driven B cell production of Ig. However, IL-10, when added exogenously, significantly enhanced the helper activity of CD57(+ )GC-Th cells, while TGF-β1 completely and IFN-γ partially suppressed the CD57(+ )GC-Th cell-driven Ig production. CONCLUSIONS: CD57(+)CD4(+ )T cells in the germinal centers of human lymphoid tissues are the major T helper cell subset for GC-B cells in Ig synthesis. Their helper activity is consistent with their capacity to induce AID and class switch recombination, and can be regulated by CD40L, IL-4, IL-10 and TGF-β
Evolving Networks with Multi-species Nodes and Spread in the Number of Initial Links
We consider models for growing networks incorporating two effects not
previously considered: (i) different species of nodes, with each species having
different properties (such as different attachment probabilities to other node
species); and (ii) when a new node is born, its number of links to old nodes is
random with a given probability distribution. Our numerical simulations show
good agreement with analytic solutions. As an application of our model, we
investigate the movie-actor network with movies considered as nodes and actors
as links.Comment: 5 pages, 5 figures, submitted to PR
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