1,625 research outputs found
Ehrenfest's Principle and the Problem of Time in Quantum Gravity
We elaborate on a proposal made by Greensite and others to solve the problem
of time in quantum gravity. The proposal states that a viable concept of time
and a sensible inner product can be found from the demand for the Ehrenfest
equations to hold in quantum gravity. We derive and discuss in detail exact
consistency conditions from both Ehrenfest equations as well as from the
semiclassical approximation. We also discuss consistency conditions arising
from the full field theory. We find that only a very restricted class of
solutions to the Wheeler-DeWitt equation fulfills all consistency conditions.
We conclude that therefore this proposal must either be abandoned as a means to
solve the problem of time or, alternatively, be used as an additional boundary
condition to select physical solutions from the Wheeler-DeWitt equation.Comment: 20 pages, LATE
Life-history and hormonal control of aggression in black redstarts: blocking testosterone does not decrease territorial aggression, but changes the emphasis of vocal behaviours during simulated territorial intrusions
Introduction:
Many studies in behavioural endocrinology attempt to link territorial aggression with testosterone, but the exact relationship between testosterone and territorial behaviour is still unclear and may depend on the ecology of a species. The degree to which testosterone facilitates territorial behaviour is particularly little understood in species that defend territories during breeding and outside the breeding season, when plasma levels of testosterone are low. Here we suggest that species that defend territories in contexts other than reproduction may have lost the direct regulation of territorial behaviour by androgens even during the breeding season. In such species, only those components of breeding territoriality that function simultaneously as sexually selected signals may be under control of sex steroids.<p></p>
Results:
We investigated black redstarts (Phoenicurus ochruros), a species that shows periods of territoriality within and outside of the breeding season. We treated territorial males with an anti-androgen and an aromatase inhibitor during the breeding season to block both the direct and indirect effects of testosterone. Three and ten days after the treatment, implanted males were challenged with a simulated territorial intrusion. The treatment did not reduce the overall territorial response, but it changed the emphasis of territoriality: experimental males invested more in behaviours addressed directly towards the intruder, whereas placebo-treated males put most effort into their vocal response, a component of territoriality that may be primarily directed towards their mating partner rather than the male opponent.<p></p>
Conclusions:
In combination with previous findings, these data suggest that overall territoriality may be decoupled from testosterone in male black redstarts. However, high levels of testosterone during breeding may facilitate-context dependent changes in song
Dielectric relaxation of the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate: microwave and far-IR properties
Dielectric relaxation of the ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate (EMI+ETS–), is studied using molecular dynamics (MD) simulations. The collective dynamics of polarization arising from cations and anions are examined. Characteristics of the rovibrational and translational components of polarization dynamics are analyzed to understand their respective roles in the microwave and terahertz regions of dielectric relaxation. The MD results are compared with the experimental low-frequency spectrum of EMI+ETS–, obtained via ultrafast optical Kerr effect (OKE) measurements
On the conformally coupled scalar field quantum cosmology
We propose a new initial condition for the homogeneous and isotropic quantum
cosmology, where the source of the gravitational field is a conformally coupled
scalar field, and the maximally symmetric hypersurfaces have positive
curvature. After solving corresponding Wheeler-DeWitt equation, we obtain exact
solutions in both classical and quantum levels. We propose appropriate initial
condition for the wave packets which results in a complete classical and
quantum correspondence. These wave packets closely follow the classical
trajectories and peak on them. We also quantify this correspondence using
de-Broglie Bohm interpretation of quantum mechanics. Using this proposal, the
quantum potential vanishes along the Bohmian paths and the classical and
Bohmian trajectories coincide with each other. We show that the model contains
singularities even at the quantum level. Therefore, the resulting wave packets
closely follow the classical trajectories from big-bang to big-crunch.Comment: 14 pages, 4 figures, to appear in PL
New Asymptotic Expanstion Method for the Wheeler-DeWitt Equation
A new asymptotic expansion method is developed to separate the Wheeler-DeWitt
equation into the time-dependent Schr\"{o}dinger equation for a matter field
and the Einstein-Hamilton-Jacobi equation for the gravitational field including
the quantum back-reaction of the matter field. In particular, the nonadiabatic
basis of the generalized invariant for the matter field Hamiltonian separates
the Wheeler-DeWitt equation completely in the asymptotic limit of
approaching infinity. The higher order quantum corrections of the gravity to
the matter field are found. The new asymptotic expansion method is valid
throughout all regions of superspace compared with other expansion methods with
a certain limited region of validity. We apply the new asymptotic expansion
method to the minimal FRW universe.Comment: 24 pages of Latex file, revte
Removal of Confined Ionic Liquid from a Metal Organic Framework by Extraction with Molecular Solvents
This work was supported in part by NSF Grant No. CHE-1223988 and by EPSRC Grant No. EP/K00090X/1.Peer reviewedPostprin
Testosterone affects song modulation during simulated territorial intrusions in male black redstarts (Phoenicurus ochruros)
Although it has been suggested that testosterone plays an important role in resource allocation for competitive behavior, details of the interplay between testosterone, territorial aggression and signal plasticity are largely unknown. Therefore, we investigated if testosterone acts specifically on signals that communicate the motivation or ability of individuals to engage in competitive situations in a natural context. We studied the black redstart, a territorial songbird species, during two different life-cycle stages, the early breeding phase in spring and the non-breeding phase in fall. Male territory holders were implanted with the androgen receptor blocker flutamide (Flut) and the aromatase inhibitor letrozole (Let) to inhibit the action of testosterone and its estrogenic metabolites. Controls received a placebo treatment. Three days after implantation birds were challenged with a simulated territorial intrusion (STI). Song was recorded before, during and after the challenge. In spring, both treatment groups increased the number of elements sung in parts of their song in response to the STI. However, Flut/Let-implanted males reacted to the STI with a decreased maximum acoustic frequency of one song part, while placebo-implanted males did not. Instead, placebo-implanted males sang the atonal part of their song with a broader frequency range. Furthermore, placebo-, but not Flut/Let-implanted males, sang shorter songs with shorter pauses between parts in the STIs. During simulated intrusions in fall, when testosterone levels are naturally low in this species, males of both treatment groups sang similar to Flut/Let-implanted males during breeding. The results suggest that song sung during a territorial encounter is of higher competitive value than song sung in an undisturbed situation and may, therefore, convey information about the motivation or quality of the territory holder. We conclude that testosterone facilitates context-dependent changes in song structures that may be honest signals of male quality in black redstarts
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