11,503 research outputs found
Domain walls of high-density QCD
We show that in very dense quark matter there must exist metastable domain
walls where the axial U(1) phase of the color-superconducting condensate
changes by 2pi. The decay rate of the domain walls is exponentially suppressed
and we compute it semiclassically. We give an estimate of the critical chemical
potential above which our analysis is under theoretical control.Comment: 4 pages; Eq. (16) corrected, 2 new references added, published
versio
Generating topological order from a 2D cluster state using a duality mapping
In this paper we prove, extend and review possible mappings between the
two-dimensional Cluster state, Wen's model, the two-dimensional Ising chain and
Kitaev's toric code model. We introduce a two-dimensional duality
transformation to map the two-dimensional lattice cluster state into the
topologically-ordered Wen model. Then, we subsequently investigates how this
mapping could be achieved physically, which allows us to discuss the rate at
which a topologically ordered system can be achieved. Next, using a lattice
fermionization method, Wen's model is mapped into a series of one-dimensional
Ising interactions. Considering the boundary terms with this mapping then
reveals how the Ising chains interact with one another. The relationships
discussed in this paper allow us to consider these models from two different
perspectives: From the perspective of condensed matter physics these mappings
allow us to learn more about the relation between the ground state properties
of the four different models, such as their entanglement or topological
structure. On the other hand, we take the duality of these models as a starting
point to address questions related to the universality of their ground states
for quantum computation.Comment: 5 Figure
Spontaneous Symmetry Breaking with Abnormal Number of Nambu-Goldstone Bosons and Kaon Condensate
We describe a class of relativistic models incorporating finite density of
matter in which spontaneous breakdown of continuous symmetries leads to a
lesser number of Nambu-Goldstone bosons than that required by the Goldstone
theorem. This class, in particular, describes the dynamics of the kaon
condensate in the color-flavor locked phase of high density QCD. We describe
the spectrum of low energy excitations in this dynamics and show that, despite
the presence of a condensate and gapless excitations, this system is not a
superfluid.Comment: 5 pages, 1 figure, REVTeX. Minor revisions made and 2 new references
added. To appear in Phys. Rev. Let
Swinging of red blood cells under shear flow
We reveal that under moderate shear stress (of the order of 0.1 Pa) red blood
cells present an oscillation of their inclination (swinging) superimposed to
the long-observed steady tanktreading (TT) motion. A model based on a fluid
ellipsoid surrounded by a visco-elastic membrane initially unstrained (shape
memory) predicts all observed features of the motion: an increase of both
swinging amplitude and period (1/2 the TT period) upon decreasing the shear
stress, a shear stress-triggered transition towards a narrow shear stress-range
intermittent regime of successive swinging and tumbling, and a pure tumbling
motion at lower shear stress-values.Comment: 4 pages 5 figures submitted to Physical Review Letter
Decay of scalar turbulence revisited
We demonstrate that at long times the rate of passive scalar decay in a
turbulent, or simply chaotic, flow is dominated by regions (in real space or in
inverse space) where mixing is less efficient. We examine two situations. The
first is of a spatially homogeneous stationary turbulent flow with both viscous
and inertial scales present. It is shown that at large times scalar
fluctuations decay algebraically in time at all spatial scales (particularly in
the viscous range, where the velocity is smooth). The second example explains
chaotic stationary flow in a disk/pipe. The boundary region of the flow
controls the long-time decay, which is algebraic at some transient times, but
becomes exponential, with the decay rate dependent on the scalar diffusion
coefficient, at longer times.Comment: 4 pages, no figure
Pion Propagation near the QCD Chiral Phase Transition
We point out that, in analogy with spin waves in antiferromagnets, all
parameters describing the real-time propagation of soft pions at temperatures
below the QCD chiral phase transition can be expressed in terms of static
correlators. This allows, in principle, the determination of the soft pion
dispersion relation on the lattice. Using scaling and universality arguments,
we determine the critical behavior of the parameters of pion propagation. We
predict that when the critical temperature is approached from below, the pole
mass of the pion drops despite the growth of the pion screening mass. This fact
is attributed to the decrease of the pion velocity near the phase transition.Comment: 8 pages (single column), RevTeX; added references, version to be
published in PR
Expansion of Major Urban Areas in the US Great Plains from 2000 to 2009 Using Satellite Scatterometer Data
A consistent dataset delineating and characterizing changes in urban environments will be valuable for socioeconomic and environmental research and for sustainable urban development. Remotely sensed data have been long used to map urban extent and infrastructure at various spatial and spectral resolutions. Although many datasets and approaches have been tried, there is not yet a universal way to map urban extents across the world. Here we combined a microwave scatterometer (QuikSCAT) dataset at ~1 km posting with percent impervious surface area (%ISA) data from the National Land Cover Dataset (NLCD) that was generated from Landsat data, and ambient population data from the LandScan product to characterize and quantify growth in nine major urban areas in the US Great Plains from 2000 to 2009. Nonparametric Mann-Kendall trend tests on backscatter time series from urban areas show significant expanding trends in eight of nine urban areas with p-values ranging 0.032 to 0.001. The sole exception is Houston, which has a substantial non-urban backscatter at the northeastern edge of the urban core. Strong power law scaling relationships between ambient population and either urban area or backscatter power (r2 of 0.96 in either model) with sub-linear exponents (β of 0.911 and 0.866, respectively) indicate urban areas become more compact with more vertical built-up structure than lateral expansion to accommodate the increased population. Increases in backscatter and %ISA datasets between 2001 and 2006 show agreement in both magnitude and direction for all urban areas except Minneapolis-St. Paul (MSP), likely due to the presence of many lakes and ponds throughout the MSP metropolitan area. We conclude discussing complexities in the backscatter data caused by large metal structures and rainfall
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