4,829 research outputs found
Lower bound for the Poisson bracket invariant on surfaces
Recently, L. Buhovsky, A. Logunov and S. Tanny proved the (strong) Poisson
bracket conjecture by Leonid Polterovich in dimension 2. In this note, instead
of open cover constituted of displaceable sets in their work, considering open
cover constituted of topological discs we give a sufficient and necessary
condition that Poisson bracket invariants of these covers are positive.Comment: 10 page
Quantization Noise Shaping for Information Maximizing ADCs
ADCs sit at the interface of the analog and digital worlds and fundamentally
determine what information is available in the digital domain for processing.
This paper shows that a configurable ADC can be designed for signals with non
constant information as a function of frequency such that within a fixed power
budget the ADC maximizes the information in the converted signal by frequency
shaping the quantization noise. Quantization noise shaping can be realized via
loop filter design for a single channel delta sigma ADC and extended to common
time and frequency interleaved multi channel structures. Results are presented
for example wireline and wireless style channels.Comment: 4 pages, 6 figure
Plasmon geometric phase and plasmon Hall shift
The collective plasmonic modes of a metal comprise a pattern of charge
density and tightly-bound electric fields that oscillate in lock-step to yield
enhanced light-matter interaction. Here we show that metals with non-zero Hall
conductivity host plasmons with a fine internal structure: they are
characterized by a current density configuration that sharply departs from that
of ordinary zero Hall conductivity metals. This non-trivial internal structure
dramatically enriches the dynamics of plasmon propagation, enabling plasmon
wavepackets to acquire geometric phases as they scatter. Strikingly, at
boundaries these phases accumulate allowing plasmon waves that reflect off to
experience a non-reciprocal parallel shift along the boundary displacing the
incident and reflected plasmon trajectories. This plasmon Hall shift, tunable
by Hall conductivity as well as plasmon wavelength, displays the chirality of
the plasmon's current distribution and can be probed by near-field photonics
techniques. Anomalous plasmon dynamics provide a real-space window into the
inner structure of plasmon bands, as well as new means for directing plasmonic
beams
Large optical conductivity of Dirac semimetal Fermi arc surfaces states
Fermi arc surface states, a hallmark of topological Dirac semimetals, can
host carriers that exhibit unusual dynamics distinct from that of their parent
bulk. Here we find that Fermi arc carriers in intrinsic Dirac semimetals
possess a strong and anisotropic light matter interaction. This is
characterized by a large Fermi arc optical conductivity when light is polarized
transverse to the Fermi arc; when light is polarized along the Fermi arc, Fermi
arc optical conductivity is significantly muted. The large surface spectral
weight is locked to the wide separation between Dirac nodes and persists as a
large Drude weight of Fermi arc carriers when the system is doped. As a result,
large and anisotropic Fermi arc conductivity provides a novel means of
optically interrogating the topological surfaces states of Dirac semimetals.Comment: 8 pages, 3 figure
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