12,878 research outputs found
Blackbody Radiation and the Scaling Symmetry of Relativistic Classical Electron Theory with Classical Electromagnetic Zero-Point Radiation
It is pointed out that relativistic classical electron theory with classical
electromagnetic zero-point radiation has a scaling symmetry which is suitable
for understanding the equilibrium behavior of classical thermal radiation at a
spectrum other than the Rayleigh-Jeans spectrum. In relativistic classical
electron theory, the masses of the particles are the only scale-giving
parameters associated with mechanics while the action-angle variables are scale
invariant. The theory thus separates the interaction of the action variables of
matter and radiation from the scale-giving parameters. Classical zero-point
radiation is invariant under scattering by the charged particles of
relativistic classical electron theory. The basic ideas of the matter
-radiation interaction are illustrated in a simple relativistic classical
electromagnetic example.Comment: 18 page
Shareholder Voting and the Chicago School: Now Is the Winter of Our Discontent
We have simulated the effect of different parameters in location-aware information sharing policies for crowd-based information exchange systems. The purpose of this simulation was to find out which parameters improved the upload time, battery life and success rate for nodes trying to upload a large file under bad conditions. To test the effect of these parameters on a larger scale, we simulated an area where a large number of nodes were moving around. Our test results showed that nodes greatly improved their battery life and the upload time by limiting the number of nodes they send data to, rather than sharing data with all nodes within reach. However, sending the oldest collected data performed very bad in regards of battery life time and had a relatively high amount of nodes that did not manage to upload their file. We concluded that nodes should not share their data with all available nodes at all times, and be restrictive in the amount of data they share with other nodes to conserve battery
Stability of Sasaki-extremal metrics under complex deformations
We consider the stability of Sasaki-extremal metrics under deformations of
the complex structure on the Reeb foliation. Given such a deformation
preserving the action of a compact subgroup of the automorphism group of a
Sasaki-extremal structure, a sufficient condition is given involving the
nondegeneracy of the relative Futaki invariant for the deformations to contain
Sasaki-extremal structures.
Deformations of Sasaki-Einstein metrics are also considered, where it
suffices that the deformation preserve a maximal torus. As an application, new
families of Sasaki-Einstein and Sasaki-extremal metrics are given on
deformations of well known 3-Sasaki 7-manifolds.Comment: Added the obstruction to the existence of Sasaki structures under
transversal complex deformations. 30 pages and 1 figur
Some Heuristic Semiclassical Derivations of the Planck Length, the Hawking Effect and the Unruh Effect
The formulae for Planck length, Hawking temperature and Unruh-Davies
temperature are derived by using only laws of classical physics together with
the Heisenberg principle. Besides, it is shown how the Hawking relation can be
deduced from the Unruh relation by means of the principle of equivalence; the
deep link between Hawking effect and Unruh effect is in this way clarified.Comment: LaTex file, 6 pages, no figure
Mapping RT-LOTOS specifications into Time Petri Nets
RT-LOTOS is a timed process algebra which enables compact
and abstract specification of real-time systems. This paper proposes and illustrates a structural translation of RT-LOTOS terms into behaviorally equivalent (timed bisimilar) finite Time Petri nets. It is therefore possible to apply Time Petri nets verification techniques to the profit of RT-LOTOS. Our approach has been implemented in RTL2TPN, a prototype tool which takes as input an RT-LOTOS specification and outputs a TPN. The latter is verified using TINA, a TPN analyzer developed by LAAS-CNRS. The toolkit made of RTL2TPN and TINA has been positively benchmarked against previously developed RT-LOTOS verification tool
Absence of Metastable States in Strained Monatomic Cubic Crystals
A tetragonal (Bain path) distortion of a metal with an fcc (bcc) ground state
will initially cause an increase in energy, but at some point along the Bain
path the energy will again decrease until a local minimum is reached. Using a
combination of parametrized tight-binding and first-principles LAPW
calculations we show that this local minimum is unstable with respect to an
elastic distortion, except in the rare case that the minimum is at the bcc
(fcc) point on the Bain path. This shows that body-centered tetragonal phases
of these materials, which have been seen in epitaxially grown thin films, must
be stabilized by the substrate and cannot be free-standing films.Comment: 7 pages, 5 postscript figures, REVTEX, submitted to Phys. Rev.
Improved Parallel Rabin-Karp Algorithm Using Compute Unified Device Architecture
String matching algorithms are among one of the most widely used algorithms
in computer science. Traditional string matching algorithms efficiency of
underlaying string matching algorithm will greatly increase the efficiency of
any application. In recent years, Graphics processing units are emerged as
highly parallel processor. They out perform best of the central processing
units in scientific computation power. By combining recent advancement in
graphics processing units with string matching algorithms will allows to speed
up process of string matching. In this paper we proposed modified parallel
version of Rabin-Karp algorithm using graphics processing unit. Based on that,
result of CPU as well as parallel GPU implementations are compared for
evaluating effect of varying number of threads, cores, file size as well as
pattern size.Comment: Information and Communication Technology for Intelligent Systems
(ICTIS 2017
Gravity and the Quantum Vacuum Inertia Hypothesis
In previous work it has been shown that the electromagnetic quantum vacuum,
or electromagnetic zero-point field, makes a contribution to the inertial
reaction force on an accelerated object. We show that the result for inertial
mass can be extended to passive gravitational mass. As a consequence the weak
equivalence principle, which equates inertial to passive gravitational mass,
appears to be explainable. This in turn leads to a straightforward derivation
of the classical Newtonian gravitational force. We call the inertia and
gravitation connection with the vacuum fields the quantum vacuum inertia
hypothesis. To date only the electromagnetic field has been considered. It
remains to extend the hypothesis to the effects of the vacuum fields of the
other interactions. We propose an idealized experiment involving a cavity
resonator which, in principle, would test the hypothesis for the simple case in
which only electromagnetic interactions are involved. This test also suggests a
basis for the free parameter which we have previously defined to
parametrize the interaction between charge and the electromagnetic zero-point
field contributing to the inertial mass of a particle or object.Comment: 18 pages, no figures. Annalen der Physik, 2005, in press. New version
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Solid-state photonic interfaces using semiconductor quantum dots
New technologies based on the properties of quantum mechanics promise
to revolutionise the way information is processed by outperforming what is
possible using classical devices. Examples include massively parallel processing
using quantum computers, verifiably secure communication using quantum
cryptography, and measurement with sensitivity beyond classical limitation
with quantum metrology. Realising the full potential of these technologies
necessitates the ability to communicate quantum information over large
distances, a key requirement for future quantum networks. However, developing
practical implementations of long-distance quantum communication
is challenging as it necessitates three major ingredients: light-matter interfaces,
elementary quantum operations, and quantum memories. This thesis
describes work that has been undertaken to address these requirements using
semiconductor nanotechnology.
We have first demonstrated that single InAs quantum dots embedded inside
conventional diode structures constitute high-fidelity controllable interfaces
between optical qubits and solid-state qubits. Indeed, the polarisation
state of a photon was transferred into the spin state of an electron-hole pair
and eventually restored through radiative recombination of the electron and
the hole with a fidelity up to 95%. Moreover, spins were manipulated using
subnanosecond modulation of a vertical electric field applied to the quantum
dots. By controlling this electrical modulation, we demonstrated elementary
phase-shift and spin-flip gate operations with near-unity fidelities.
An electron-hole pair confi ned in a single quantum dot has a short radiative
lifetime limiting therefore its use as an excitonic quantum memory.
The solution we proposed was to use a quantum dot molecule to control the
spatial separation of the electron and the hole and therefore prevent their
recombination. Comprehensive studies of electric field eff ects upon the photoluminescence
of quantum dot molecules lead to a clear understanding and
a good control over their physical properties. Single photons were stored in
individual quantum dot molecules up to 1μs and read out on a subnanosecond time scale. Moreover, the circular polarisation of individual photons was
transferred into the spin state of electron-hole pairs with a fidelity above
90%, which does not degrade for storage times up to the 12.5 ns repetition
period of the experiment.
Our work on single quantum dots could be extended in the near future to
allow for two-qubits quantum operations by con fining a second electron-hole
pair to be electrically manipulated. Storage of a superposition of spin states
in a quantum dot molecule should also be possible if the spin states are made
degenerate, which is feasible using the electric fi eld dependence of the energy
splitting between the spin states discussed in this thesis. We believe that
combining both approaches will lead to the development of a controllable
multi-qubit quantum memory for polarised light, a building block for long distance
quantum communication based on semiconductor nanotechnology
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