15,261 research outputs found
Complex structures and the Elie Cartan approach to the theory of spinors
Each isometric complex structure on a 2-dimensional euclidean space
corresponds to an identification of the Clifford algebra of with the
canonical anticommutation relation algebra for ( fermionic) degrees of
freedom. The simple spinors in the terminology of E.~Cartan or the pure spinors
in the one of C. Chevalley are the associated vacua. The corresponding states
are the Fock states (i.e. pure free states), therefore, none of the above
terminologies is very good.Comment: 10
A Fintech Approach Towards Resolving the Young Adult Home Ownership Challenge
Housing prices globally remain very expensive for young adults while financial instruments to obtain them become more complicated, demanding, and discouraging, especially in the modern post global financial crisis (2007–2017). The way people acquire homes haven’t change over the last 100 years, maintaining the three classic and dominant alternatives which is either thorough mortgages, cash payments, or combination of these. Young adults have been underserved by financial institutions and their products have not yet met young adults’ conditions. This research has been directed to utilize today’s technology and contribute with innovative financing solutions that can addresses the young adults’ needs. The proposed Fintech approach presents the architecture of a technology-based platform whereby Co-sharing agreements between real estate developers and young adults can be created. Such agreements can be integrated into the financial institutions processes to efficiently address and serve this significant target group by delivering creative innovative financing alternatives
Ultra-low phase noise all-optical microwave generation setup based on commercial devices
In this paper, we present a very simple design based on commercial devices
for the all-optical generation of ultra-low phase noise microwave signals. A
commercial, fibered femtosecond laser is locked to a laser that is stabilized
to a commercial ULE Fabry-Perot cavity. The 10 GHz microwave signal extracted
from the femtosecond laser output exhibits a single sideband phase noise
at 1 Hz Fourier frequency, at
the level of the best value obtained with such "microwave photonics" laboratory
experiments \cite{Fortier2011}. Close-to-the-carrier ultra-low phase noise
microwave signals will now be available in laboratories outside the frequency
metrology field, opening up new possibilities in various domains.Comment: 8 pages, 3 figures. To be published in Applied Optics, early posting
version available at
http://www.opticsinfobase.org/ao/upcoming_pdf.cfm?id=23114
Vibrational dynamics of confined granular material
By means of two-dimensional contact dynamics simulations, we analyze the
vibrational dynamics of a confined granular layer in response to harmonic
forcing. We use irregular polygonal grains allowing for strong variability of
solid fraction. The system involves a jammed state separating passive (loading)
and active (unloading) states. We show that an approximate expression of the
packing resistance force as a function of the displacement of the free
retaining wall from the jamming position provides a good description of the
dynamics. We study in detail the scaling of displacements and velocities with
loading parameters. In particular, we find that, for a wide range of
frequencies, the data collapse by scaling the displacements with the inverse
square of frequency, the inverse of the force amplitude and the square of
gravity. Interestingly, compaction occurs during the extension of the packing,
followed by decompaction in the contraction phase. We show that the mean
compaction rate increases linearly with frequency up to a characteristic
frequency and then it declines in inverse proportion to frequency. The
characteristic frequency is interpreted in terms of the time required for the
relaxation of the packing through collective grain rearrangements between two
equilibrium states
Damping rate of plasmons and photons in a degenerate nonrelativistic plasma
A calculation is presented of the plasmon and photon damping rates in a dense
nonrelativistic plasma at zero temperature, following the resummation program
of Braaten-Pisarski. At small soft momentum , the damping is dominated by scattering processes corresponding to double longitudinal Landau
damping. The dampings are proportional to , where
is the Fermi velocity.Comment: 9 pages, 2 figure
Spin glass behavior in an interacting gamma-Fe2O3 nanoparticle system
In this paper we investigate the superspin glass behavior of a concentrated
assembly of interacting maghemite nanoparticles and compare it to that of
canonical atomic spin glass systems. ac versus temperature and frequency
measurements show evidence of a superspin glass transition taking place at low
temperature. In order to fully characterize the superspin glass phase, the
aging behavior of both the thermo-remanent magnetization (TRM) and ac
susceptibility has been investigated. It is shown that the scaling laws obeyed
by superspin glasses and atomic spin glasses are essentially the same, after
subtraction of a superparamagnetic contribution from the superspin glass
response functions. Finally, we discuss a possible origin of this
superparamagnetic contribution in terms of dilute spin glass models
N-complexes as functors, amplitude cohomology and fusion rules
We consider N-complexes as functors over an appropriate linear category in
order to show first that the Krull-Schmidt Theorem holds, then to prove that
amplitude cohomology only vanishes on injective functors providing a well
defined functor on the stable category. For left truncated N-complexes, we show
that amplitude cohomology discriminates the isomorphism class up to a
projective functor summand. Moreover amplitude cohomology of positive
N-complexes is proved to be isomorphic to an Ext functor of an indecomposable
N-complex inside the abelian functor category. Finally we show that for the
monoidal structure of N-complexes a Clebsch-Gordan formula holds, in other
words the fusion rules for N-complexes can be determined.Comment: Final versio
Force chains and contact network topology in packings of elongated particles
By means of contact dynamic simulations, we investigate the contact network
topology and force chains in two-dimensional packings of elongated particles
modeled by rounded-cap rectangles. The morphology of large packings of
elongated particles in quasistatic equilibrium is complex due to the combined
effects of local nematic ordering of the particles and orientations of contacts
between particles. We show that particle elongation affects force distributions
and force/fabric anisotropy via various local structures allowed by steric
exclusions and the requirement of force balance. As a result, the force
distributions become increasingly broader as particles become more elongated.
Interestingly, the weak force network transforms from a passive stabilizing
agent with respect to strong force chains to an active force-transmitting
network for the whole system. The strongest force chains are carried by
side/side contacts oriented along the principal stress direction.Comment: Soumis a Physical Review
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