1,331 research outputs found
Euler characteristic and quadrilaterals of normal surfaces
Let be a compact 3-manifold with a triangulation . We give an
inequality relating the Euler characteristic of a surface normally embedded
in with the number of normal quadrilaterals in . This gives a relation
between a topological invariant of the surface and a quantity derived from its
combinatorial description. Secondly, we obtain an inequality relating the
number of normal triangles and normal quadrilaterals of , that depends on
the maximum number of tetrahedrons that share a vertex in .Comment: 7 pages, 1 figur
Luminary 1B DAP preflight performance evaluation
Preflight analysis of LUMINARY 1B DAP simulation and performance testing for Apollo Mission H
Field quantization for chaotic resonators with overlapping modes
Feshbach's projector technique is employed to quantize the electromagnetic
field in optical resonators with an arbitray number of escape channels. We find
spectrally overlapping resonator modes coupled due to the damping and noise
inflicted by the external radiation field. For wave chaotic resonators the mode
dynamics is determined by a non--Hermitean random matrix. Upon including an
amplifying medium, our dynamics of open-resonator modes may serve as a starting
point for a quantum theory of random lasing.Comment: 4 pages, 1 figur
A loss measurement system in a test facility for high-current superconducting cables and wires
The AC loss measurement system in the Twente test facility is operational. Preliminary results of the first loss measurements on a vacuum-welded conductor are presented. The Twente test facility is a high-current system in which superconductors can be tested up to 7 T and 25 kA. The loss measurements were done on a monolith conductor designed for TORE SUPRA, manufactured by Vacuumschmelze
The role of the electromagnetic field in the formation of domains in the process of symmetry breaking phase transitions
In the framework of quantum field theory we discuss the emergence of a phase
locking among the electromagnetic modes and the matter components on an
extended space-time region. We discuss the formation of extended domains
exhibiting in their fundamental states non-vanishing order parameters, whose
existence is not included in the Lagrangian. Our discussion is motivated by the
interest in the study of the general problem of the stability of mesoscopic and
macroscopic complex systems arising from fluctuating quantum components in
connection with the problem of defect formation during the process of
non-equilibrium symmetry breaking phase transitions characterized by an order
parameter.Comment: Physical Review A, in the pres
Steady state entanglement in open and noisy quantum systems at high temperature
We show that quantum mechanical entanglement can prevail even in noisy open
quantum systems at high temperature and far from thermodynamical equilibrium,
despite the deteriorating effect of decoherence. The system consists of a
number N of interacting quantum particles, and it can interact and exchange
particles with some environment. The effect of decoherence is counteracted by a
simple mechanism, where system particles are randomly reset to some standard
initial state, e.g. by replacing them with particles from the environment. We
present a master equation that describes this process, which we can solve
analytically for small N. If we vary the interaction strength and the reset
against decoherence rate, we find a threshold below which the equilibrium state
is classically correlated, and above which there is a parameter region with
genuine entanglement.Comment: 5 pages, 3 figure
A Study on the Noise Threshold of Fault-tolerant Quantum Error Correction
Quantum circuits implementing fault-tolerant quantum error correction (QEC)
for the three qubit bit-flip code and five-qubit code are studied. To describe
the effect of noise, we apply a model based on a generalized effective
Hamiltonian where the system-environment interactions are taken into account by
including stochastic fluctuating terms in the system Hamiltonian. This noise
model enables us to investigate the effect of noise in quantum circuits under
realistic device conditions and avoid strong assumptions such as maximal
parallelism and weak storage errors. Noise thresholds of the QEC codes are
calculated. In addition, the effects of imprecision in projective measurements,
collective bath, fault-tolerant repetition protocols, and level of parallelism
in circuit constructions on the threshold values are also studied with emphasis
on determining the optimal design for the fault-tolerant QEC circuit. These
results provide insights into the fault-tolerant QEC process as well as useful
information for designing the optimal fault-tolerant QEC circuit for particular
physical implementation of quantum computer.Comment: 9 pages, 9 figures; to be submitted to Phys. Rev.
Estimation of drift and diffusion functions from time series data: A maximum likelihood framework
Complex systems are characterized by a huge number of degrees of freedom
often interacting in a non-linear manner. In many cases macroscopic states,
however, can be characterized by a small number of order parameters that obey
stochastic dynamics in time. Recently techniques for the estimation of the
corresponding stochastic differential equations from measured data have been
introduced. This contribution develops a framework for the estimation of the
functions and their respective (Bayesian posterior) confidence regions based on
likelihood estimators. In succession approximations are introduced that
significantly improve the efficiency of the estimation procedure. While being
consistent with standard approaches to the problem this contribution solves
important problems concerning the applicability and the accuracy of estimated
parameters.Comment: 18 pages, 2 figure
Effects of external global noise on the catalytic CO oxidation on Pt(110)
Oxidation reaction of CO on a single platinum crystal is a reaction-diffusion
system that may exhibit bistable, excitable, and oscillatory behavior. We
studied the effect of a stochastic signal artificially introduced into the
system through the partial pressure of CO. First, the external signal is
employed as a turbulence suppression tool, and second, it modifies the
boundaries in the bistable transition between the CO and oxygen covered phases.
Experiments using photoemission electron microscopy (PEEM) together with
numerical simulations performed with the Krischer-Eiswirth-Ertl (KEE) model are
presented.Comment: 15 pages, 7 figures, accepted in J. Chem. Phy
Correlation of optical conductivity and ARPES spectra of strong-coupling large polarons and its display in cuprates
Common approach is used to calculate band due to strong-coupling large
polaron (SCLP) photodissociation in ARPES and in optical conductivity (OC)
spectra. It is based on using the coherent-states representation for the phonon
field in SCLP. The calculated positions of both band maximums are universal
functions of one parameter - the SCLP binding energy Ep: ARPES band maximum
lies at binding energy about 3.2Ep; the OC band maximum is at the photon energy
about 4.2Ep. The half-widths of the bands are mainly determined by Ep and
slightly depend on Frohlich electron-phonon coupling constant: for its value
6-8 the ARPES band half-width is 1.7-1.3Ep and the OC band half-width is
2.8-2.2Ep. Using these results one can predict approximate position of ARPES
band maximum and half-width from the maximum of mid-IR OC band and vice versa.
Comparison of the results with experiments leads to a conclusion that
underdoped cuprates contain SCLPs with Ep=0.1-0.2 eV that is in good conformity
with the medium parameters in cuprates. The values of the polaron binding
energy determined from experimental ARPES and OC spectra of the same material
are in good conformity too: the difference between them is within 10 percent.Comment: 17 pages, 6 figure
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