51,648 research outputs found
Anomalous non-ergodic scaling in adiabatic multicritical quantum quenches
We investigate non-equilibrium dynamical scaling in adiabatic quench
processes across quantum multicritical points. Our analysis shows that the
resulting power-law scaling depends sensitively on the control path, and that
anomalous critical exponents may emerge depending on the universality class. We
argue that the observed anomalous behavior originates in the fact that the
dynamical excitation process takes place asymmetrically with respect to the
static multicritical point, and that non-critical energy modes may play a
dominant role. As a consequence, dynamical scaling requires introducing new
non-static exponents.Comment: 4 pages, 4 figures, minor change in figure
Wrinkling of Orthotropic Viscoelastic Membranes
This paper presents a simplified simulation technique for orthotropic viscoelastic films.
Wrinkling is detected by a combined stress-strain criterion and an iterative scheme searches
for the wrinkle angle using a pseudo-elastic material stiffness matrix based on a nonlinear
viscoelastic constitutive model. This simplified model has been implemented in
ABAQUS/Explicit and is able to compute the behavior of a membrane structure by superposition
of a small number of response increments. The model has been tested against
a published solution for a time-independent isotropic membrane under simple shear and
also against experimental results on StratoFilm 420 under simple shear
Dynamical critical scaling and effective thermalization in quantum quenches: the role of the initial state
We explore the robustness of universal dynamical scaling behavior in a
quantum system near criticality with respect to initialization in a large class
of states with finite energy. By focusing on a homogeneous XY quantum spin
chain in a transverse field, we characterize the non-equilibrium response under
adiabatic and sudden quench processes originating from a pure as well as a
mixed excited initial state, and involving either a regular quantum critical or
a multicritical point. We find that the critical exponents of the ground-state
quantum phase transition can be encoded in the dynamical scaling exponents
despite the finite energy of the initial state. In particular, we identify
conditions on the initial distribution of quasi-particle excitation which
ensure Kibble-Zurek scaling to persist. The emergence of effective thermal
equilibrium behavior following a sudden quench towards criticality is also
investigated, with focus on the long-time dynamics of the quasi-particle
excitation. For a quench to a regular quantum critical point, this observable
is found to behave thermally provided that the system is prepared at
sufficiently high temperature, whereas thermalization fails to occur in
quenches taking the system towards a multi-critical point. We argue that the
observed lack of thermalization originates in this case in the asymmetry of the
impulse region that is also responsible for anomalous multicritical dynamical
scaling.Comment: 18 pages, 13 eps color figures, published versio
73 GHz Wideband Millimeter-Wave Foliage and Ground Reflection Measurements and Models
This paper presents 73 GHz wideband outdoor foliage and ground reflection
measurements. Propagation measurements were made with a 400 Megachip-per-second
sliding correlator channel sounder, with rotatable 27 dBi (7 degrees half-
power beamwidth) horn antennas at both the transmitter and receiver, to study
foliage-induced scattering and de-polarization effects, to assist in developing
future wireless systems that will use adaptive array antennas. Signal
attenuation through foliage was measured to be 0.4 dB/m for both co- and
cross-polarized antenna configurations. Measured ground reflection coefficients
for dirt and gravel ranged from 0.02 to 0.34, for incident angles ranging from
60 degrees to 81 degrees (with respect to the normal incidence of the surface).
These data are useful for link budget design and site-specific (ray-tracing)
models for future millimeter-wave communication systems.Comment: 6 pages, 4 figures, 2015 IEEE International Conference on
Communications (ICC), ICC Workshop
Local discontinuous Galerkin methods for fractional ordinary differential equations
This paper discusses the upwinded local discontinuous Galerkin methods for
the one-term/multi-term fractional ordinary differential equations (FODEs). The
natural upwind choice of the numerical fluxes for the initial value problem for
FODEs ensures stability of the methods. The solution can be computed element by
element with optimal order of convergence in the norm and
superconvergence of order at the downwind point of each
element. Here is the degree of the approximation polynomial used in an
element and () represents the order of the one-term
FODEs. A generalization of this includes problems with classic 'th-term
FODEs, yielding superconvergence order at downwind point as
. The underlying mechanism of the
superconvergence is discussed and the analysis confirmed through examples,
including a discussion of how to use the scheme as an efficient way to evaluate
the generalized Mittag-Leffler function and solutions to more generalized
FODE's.Comment: 17 pages, 7 figure
- âŠ