3,849 research outputs found
A density-functional theory study of the confined soft ellipsoid fluid
A system of soft ellipsoid molecules confined between two planar walls is studied using classical density-functional theory. Both the isotropic and nematic phases are considered. The excess free energy is evaluated using two different Ansätze and the intermolecular interaction is incorporated using two different direct correlation functions (DCF’s). The first is a numerical DCF obtained from simulations of bulk soft ellipsoid fluids and the second is taken from the Parsons–Lee theory. In both the isotropic and nematic phases the numerical DCF gives density and order parameter profiles in reasonable agreement with simulation. The Parsons–Lee DCF also gives reasonable agreement in the isotropic phase but poor agreement in the nematic phase
Contextual advantage for state discrimination
Finding quantitative aspects of quantum phenomena which cannot be explained
by any classical model has foundational importance for understanding the
boundary between classical and quantum theory. It also has practical
significance for identifying information processing tasks for which those
phenomena provide a quantum advantage. Using the framework of generalized
noncontextuality as our notion of classicality, we find one such nonclassical
feature within the phenomenology of quantum minimum error state discrimination.
Namely, we identify quantitative limits on the success probability for minimum
error state discrimination in any experiment described by a noncontextual
ontological model. These constraints constitute noncontextuality inequalities
that are violated by quantum theory, and this violation implies a quantum
advantage for state discrimination relative to noncontextual models.
Furthermore, our noncontextuality inequalities are robust to noise and are
operationally formulated, so that any experimental violation of the
inequalities is a witness of contextuality, independently of the validity of
quantum theory. Along the way, we introduce new methods for analyzing
noncontextuality scenarios, and demonstrate a tight connection between our
minimum error state discrimination scenario and a Bell scenario.Comment: 18 pages, 9 figure
First record of Spilomena mocsaryi Kohl, 1898 (Hymenoptera) from Malta with a check-list of Maltese Crabronidae
Until now the Crabronidae fauna of the Maltese Islands comprised 45 species in 5 subfamilies. Recently, one of us (EX) while studying insect visitors on flowers of Capparis orientalis found a new crabronid species from Malta, Spilomena mocsaryi Kohl, 1898. A check-list of the 46 species of Crabronidae so far recorded from the Maltese Islands is provided.peer-reviewe
The Catenary Degree of Krull Monoids I
Let be a Krull monoid with finite class group such that every class
contains a prime divisor (for example, a ring of integers in an algebraic
number field or a holomorphy ring in an algebraic function field). The catenary
degree of is the smallest integer with the following
property: for each and each two factorizations of , there
exist factorizations of such that, for each , arises from by replacing at most atoms from
by at most new atoms. Under a very mild condition on the
Davenport constant of , we establish a new and simple characterization of
the catenary degree. This characterization gives a new structural understanding
of the catenary degree. In particular, it clarifies the relationship between
and the set of distances of and opens the way towards
obtaining more detailed results on the catenary degree. As first applications,
we give a new upper bound on and characterize when
Bayesian Inference of the Multi-Period Optimal Portfolio for an Exponential Utility
We consider the estimation of the multi-period optimal portfolio obtained by
maximizing an exponential utility. Employing Jeffreys' non-informative prior
and the conjugate informative prior, we derive stochastic representations for
the optimal portfolio weights at each time point of portfolio reallocation.
This provides a direct access not only to the posterior distribution of the
portfolio weights but also to their point estimates together with uncertainties
and their asymptotic distributions. Furthermore, we present the posterior
predictive distribution for the investor's wealth at each time point of the
investment period in terms of a stochastic representation for the future wealth
realization. This in turn makes it possible to use quantile-based risk measures
or to calculate the probability of default. We apply the suggested Bayesian
approach to assess the uncertainty in the multi-period optimal portfolio by
considering assets from the FTSE 100 in the weeks after the British referendum
to leave the European Union. The behaviour of the novel portfolio estimation
method in a precarious market situation is illustrated by calculating the
predictive wealth, the risk associated with the holding portfolio, and the
default probability in each period.Comment: 38 pages, 5 figure
Zero-sum problems with congruence conditions
For a finite abelian group and a positive integer , let denote the smallest integer such that
every sequence over of length has a nonempty zero-sum
subsequence of length . We determine for all when has rank at most two and, under mild
conditions on , also obtain precise values in the case of -groups. In the
same spirit, we obtain new upper bounds for the Erd{\H o}s--Ginzburg--Ziv
constant provided that, for the -subgroups of , the Davenport
constant is bounded above by . This
generalizes former results for groups of rank two
REDO RSVP: Efficient Signalling for Multimedia in the Internet
Alarming reports of performance and scalability problems associated with per-flow reservations, have led many to lose belief in RSVP and the Integrated Services Architecture that relies on it. Because we are convinced of the need for some form of resource reservation, to support multimedia communications in the Internet, we have set about trying to improve RSVP. By careful study of the protocol, we have identified areas for improvement, and propose REDO RSVP, a reduced overhead version that includes a fast establishment mechanism (FEM). In this paper we describe the rationale for REDO RSVP and present a detailed analysis of its features and operations. We also analyse REDO RSVP by means of simulations, and show that it offers improvements to the performance of RSVP
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