70,218 research outputs found
The incomplete beta function law for parallel tempering sampling of classical canonical systems
We show that the acceptance probability for swaps in the parallel tempering
Monte Carlo method for classical canonical systems is given by a universal
function that depends on the average statistical fluctuations of the potential
and on the ratio of the temperatures. The law, called the incomplete beta
function law, is valid in the limit that the two temperatures involved in swaps
are close to one another. An empirical version of the law, which involves the
heat capacity of the system, is developed and tested on a Lennard-Jones
cluster. We argue that the best initial guess for the distribution of
intermediate temperatures for parallel tempering is a geometric progression and
we also propose a technique for the computation of optimal temperature
schedules. Finally, we demonstrate that the swap efficiency of the parallel
tempering method for condensed-phase systems decreases naturally to zero at
least as fast as the inverse square root of the dimensionality of the physical
system.Comment: 11 pages, 4 figures; minor changes; to appear in J. Chem. Phy
Combinatorial Formulas for Macdonald and Hall-Littlewood Polynomials of Types A and C. Extended Abstract
A breakthrough in the theory of (type A) Macdonald polynomials is due to
Haglund, Haiman and Loehr, who exhibited a combinatorial formula for these
polynomials in terms of fillings of Young diagrams. Recently, Ram and Yip gave
a formula for the Macdonald polynomials of arbitrary type in terms of the
corresponding affine Weyl group. In this paper, we show that a
Haglund-Haiman-Loehr type formula follows naturally from the more general
Ram-Yip formula, via compression. Then we extend this approach to the
Hall-Littlewood polynomials of type C, which are specializations of the
corresponding Macdonald polynomials at q=0. We note that no analog of the
Haglund-Haiman-Loehr formula exists beyond type A, so our work is a first step
towards finding such a formula
Optimal prediction of folding rates and transition state placement from native state geometry
A variety of experimental and theoretical studies have established that the
folding process of monomeric proteins is strongly influenced by the topology of
the native state. In particular, folding times have been shown to correlate
well with the contact order, a measure of contact locality. Our investigation
focuses on identifying additional topologic properties that correlate with
experimentally measurable quantities, such as folding rates and transition
state placement, for both two- and three-state folders. The validation against
data from forty experiments shows that a particular topologic property which
measures the interdepedence of contacts, termed cliquishness or clustering
coefficient, can account with significant accuracy both for the transition
state placement and especially for folding rates, the linear correlation
coefficient being . This result can be further improved to , by
optimally combining the distinct topologic information captured by cliquishness
and contact order.Comment: Revtex, 15 pages, 8 figure
Defensa de la interpretación práctica del imperativo categórico
The article compares two different interpretations of Kant's categorical imperative −the practical and the logical one− and defends the practical one, arguing that it is superior because it rejects cases of free riding without necessarily rejecting cases of coordination or timing. The logical interpretation, on the other hand, leads to the undesirable outcome that it does not reject immoral cases of free riding, and to the desired outcome that it does not reject maxims of coordination/timing. Given that neither of them rejects maxims of coordination/timing (they are similar in that sense) and only the practical interpretation rejects free riding, the logical interpretation should be rejected.El artículo compara dos interpretaciones diferentes del imperativo categórico kantiano −la práctica y la lógica− y defiende la superioridad de la práctica debido a que rechaza los casos de free riding, sin rechazar necesariamente los casos de coordinación/tiempo. La interpretación lógica, en cambio, lleva al resultado indeseable de no rechazar casos inmorales de free riding, y al resultado deseable de rechazar las máximas de coordinación/tiempo. Dado que ninguna de las dos rechaza las máximas de coordinación/tiempo (y en este sentido son similares) y solamente la interpretación práctica rechaza los casos de free riding, debe rechazarse la interpretación lógica.Fil: Dimitriu, Cristian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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