19,120 research outputs found
Electron Monte Carlo Simulations of Nanoporous Si Thin Films -- The Influence of Pore-Edge Charges
Electron transport within nanostructures can be important to varied
engineering applications, such as thermoelectrics and nanoelectronics. In
theoretical studies, electron Monte Carlo simulations are widely used as an
alternative approach to solving the electron Boltzmann transport equation,
where the energy-dependent electron scattering, exact structure shape, and
detailed electric field distribution can be fully incorporated. In this work,
such electron Monte Carlo simulations are employed to predict the electrical
conductivity of periodic nanoporous Si films that have been widely studied for
thermoelectric applications. The focus is on the influence of pore-edge charges
on the electron transport. The results are further compared to our previous
modeling [Hao et al., J. Appl. Phys. 121, 094308 (2017)], where the pore-edge
electric field has its own scattering rate to be added to the scattering rates
of other mechanisms
Theories and Varying Fine Structure Constant
In analogy to theory, recently a new modified gravity theory, namely
the so-called theory, has been proposed to drive the current accelerated
expansion without invoking dark energy. In the present work, by extending
Bisabr's idea, we try to constrain theories with the varying fine
structure "constant", . We find that the constraints
on theories from the observational data are very
severe. In fact, they make theories almost indistinguishable from
CDM model.Comment: 12 pages, 4 figures, 1 table, revtex4; v2: discussions added, Phys.
Lett. B in press; v3: published versio
Satellite Broadcasting Enabled Blockchain Protocol: A Preliminary Study
Low throughput has been the biggest obstacle of large-scale blockchain
applications. During the past few years, researchers have proposed various
schemes to improve the systems' throughput. However, due to the inherent
inefficiency and defects of the Internet, especially in data broadcasting
tasks, these efforts all rendered unsatisfactory. In this paper, we propose a
novel blockchain protocol which utilizes the satellite broadcasting network
instead of the traditional Internet for data broadcasting and consensus tasks.
An automatic resumption mechanism is also proposed to solve the unique
communication problems of satellite broadcasting. Simulation results show that
the proposed algorithm has a lower communication cost and can greatly improve
the throughput of the blockchain system. Theoretical estimation of a satellite
broadcasting enabled blockchain system's throughput is 6,000,000 TPS with a 20
gbps satellite bandwidth.Comment: Accepted by 2020 Information Communication Technologies Conference
(ICTC 2020
Algebraic higher symmetry and categorical symmetry -- a holographic and entanglement view of symmetry
We introduce the notion of algebraic higher symmetry, which generalizes
higher symmetry and is beyond higher group. We show that an algebraic higher
symmetry in a bosonic system in -dimensional space is characterized and
classified by a local fusion -category. We find another way to describe
algebraic higher symmetry by restricting to symmetric sub Hilbert space where
symmetry transformations all become trivial. In this case, algebraic higher
symmetry can be fully characterized by a non-invertible gravitational anomaly
(i.e. an topological order in one higher dimension). Thus we also refer to
non-invertible gravitational anomaly as categorical symmetry to stress its
connection to symmetry. This provides a holographic and entanglement view of
symmetries. For a system with a categorical symmetry, its gapped state must
spontaneously break part (not all) of the symmetry, and the state with the full
symmetry must be gapless. Using such a holographic point of view, we obtain (1)
the gauging of the algebraic higher symmetry; (2) the classification of
anomalies for an algebraic higher symmetry; (3) the equivalence between classes
of systems, with different (potentially anomalous) algebraic higher symmetries
or different sets of low energy excitations, as long as they have the same
categorical symmetry; (4) the classification of gapped liquid phases for
bosonic/fermionic systems with a categorical symmetry, as gapped boundaries of
a topological order in one higher dimension (that corresponds to the
categorical symmetry). This classification includes symmetry protected trivial
(SPT) orders and symmetry enriched topological (SET) orders with an algebraic
higher symmetry.Comment: 61 pages, 31 figure
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