76,454 research outputs found
Ventilation of double facades
This paper deals with the development and thetesting of a simulation algorithm for the temperaturebehaviour and the flow characteristics of doublefaçades. It has been developed in order to obtain atool which enables the energy consultant to makequick design decisions without being required to usefairly complicated CFD tools.In order to determine the degree of accuracy of thealgorithm, a double façade has been monitored undercontrolled conditions and the results have beencompared against the predicted values for severaldesign situations. The resulting inaccuracy in somecases can be traced back to how the flow resistanceof various geometries are modelled. This paper deals with the development and thetesting of a simulation algorithm for the temperaturebehaviour and the flow characteristics of doublefaçades. It has been developed in order to obtain atool which enables the energy consultant to makequick design decisions without being required to usefairly complicated CFD tools.In order to determine the degree of accuracy of thealgorithm, a double façade has been monitored undercontrolled conditions and the results have beencompared against the predicted values for severaldesign situations. The resulting inaccuracy in somecases can be traced back to how the flow resistanceof various geometries are modelled
Fluctuating parts of nuclear ground state correlation energies
Background: Heavy atomic nuclei are often described using the
Hartree-Fock-Bogoliubov (HFB) method. In principle, this approach takes into
account Pauli effects and pairing correlations while other correlation effects
are mimicked through the use of effective density-dependent interactions.
Purpose: Investigate the influence of higher order correlation effects on
nuclear binding energies using Skyrme's effective interaction.
Methods: A cut-off in relative momenta is introduced in order to remove
ultraviolet divergences caused by the zero-range character of the interaction.
Corrections to binding energies are then calculated using the
quasiparticle-random-phase approximation (QRPA) and second order many-body
perturbation theory (MBPT2).
Result: Contributions to the correlation energies are evaluated for several
isotopic chains and an attempt is made to disentangle which parts give rise to
fluctuations that may be difficult to incorporate on the HFB level. The
dependence of the results on the cut-off is also investigated.
Conclusions: The improved interaction allows explicit summations of
perturbation series which is useful for the description of some nuclear
observables. However, refits of the interaction parameters are needed to obtain
more quantitative results
Proof of the Standard Quantum Limit for Monitoring Free-Mass Position
The measurement result of the moved distance for a free mass m during the
time t between two position measurements cannot be predicted with uncertainty
smaller than sqrt{hbar t/2m}. This is formulated as a standard quantum limit
(SQL) and it has been proven to always hold for the following position
measurement: a probe is set in a prescribed position before the measurement.
Just after the interaction of the mass with the probe, the probe position is
measured, and using this value, the measurement results of the pre-measurement
and post-measurement positions are estimated.Comment: 4 pages, no figur
Elements of Design for Containers and Solutions in the LinBox Library
We describe in this paper new design techniques used in the \cpp exact linear
algebra library \linbox, intended to make the library safer and easier to use,
while keeping it generic and efficient. First, we review the new simplified
structure for containers, based on our \emph{founding scope allocation} model.
We explain design choices and their impact on coding: unification of our matrix
classes, clearer model for matrices and submatrices, \etc Then we present a
variation of the \emph{strategy} design pattern that is comprised of a
controller--plugin system: the controller (solution) chooses among plug-ins
(algorithms) that always call back the controllers for subtasks. We give
examples using the solution \mul. Finally we present a benchmark architecture
that serves two purposes: Providing the user with easier ways to produce
graphs; Creating a framework for automatically tuning the library and
supporting regression testing.Comment: 8 pages, 4th International Congress on Mathematical Software, Seoul :
Korea, Republic Of (2014
Two-dimensional Copolymers and Multifractality: Comparing Perturbative Expansions, MC Simulations, and Exact Results
We analyze the scaling laws for a set of two different species of long
flexible polymer chains joined together at one of their extremities (copolymer
stars) in space dimension D=2. We use a formerly constructed field-theoretic
description and compare our perturbative results for the scaling exponents with
recent conjectures for exact conformal scaling dimensions derived by a
conformal invariance technique in the context of D=2 quantum gravity. A simple
MC simulation brings about reasonable agreement with both approaches. We
analyse the remarkable multifractal properties of the spectrum of scaling
exponents.Comment: 5 page
Unexpected systematic degeneracy in a system of two coupled Gaudin models with homogeneous couplings
We report an unexpected systematic degeneracy between different multiplets in
an inversion symmetric system of two coupled Gaudin models with homogeneous
couplings, as occurring for example in the context of solid state quantum
information processing. We construct the full degenerate subspace (being of
macroscopic dimension), which turns out to lie in the kernel of the commutator
between the two Gaudin models and the coupling term. Finally we investigate to
what extend the degeneracy is related to the inversion symmetry of the system
and find that indeed there is a large class of systems showing the same type of
degeneracy.Comment: 13 pages, 4 figure
Anomalies of weakened decoherence criteria for quantum histories
The theory of decoherent histories is checked for the requirement of
statistical independence of subsystems. Strikingly, this is satisfied only when
the decoherence functional is diagonal in both its real a n d imaginary parts.
In particular, the condition of consistency (or weak decoherence) required for
the assignment of probabilities appears to be ruled out. The same conclusion is
obtained independently, by claiming a plausible dynamical robustness of
decoherent histories.Comment: 3pp, submitted to Phys. Rev. Let
Information Transfer Implies State Collapse
We attempt to clarify certain puzzles concerning state collapse and
decoherence. In open quantum systems decoherence is shown to be a necessary
consequence of the transfer of information to the outside; we prove an upper
bound for the amount of coherence which can survive such a transfer. We claim
that in large closed systems decoherence has never been observed, but we will
show that it is usually harmless to assume its occurrence. An independent
postulate of state collapse over and above Schroedinger's equation and the
probability interpretation of quantum states, is shown to be redundant.Comment: 13 page
Using Classical Probability To Guarantee Properties of Infinite Quantum Sequences
We consider the product of infinitely many copies of a spin-
system. We construct projection operators on the corresponding nonseparable
Hilbert space which measure whether the outcome of an infinite sequence of
measurements has any specified property. In many cases, product
states are eigenstates of the projections, and therefore the result of
measuring the property is determined. Thus we obtain a nonprobabilistic quantum
analogue to the law of large numbers, the randomness property, and all other
familiar almost-sure theorems of classical probability.Comment: 7 pages in LaTe
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