1,133 research outputs found
Using Peer Grading and Proofreading to Ratchet Student Expectations in Preparing Accounting Cases
Accounting educators struggle with ways to incorporate the development of critical thinking and communication skills into the curriculum. Case analysis is one tool for developing these skills. We examine whether students’ case analysis scores improve as a result of participation in peer grading and peer review. We find that students improve their ability to perform case analyses after both evaluating and being evaluated by student peers. Students initially experience an Expectation Ratcheting learning effect after evaluating the case of a peer. Subsequently, students experience an Enhanced Feedback learning effect from the comments and suggestions made by the peers who evaluated (proofread) their cases
Chaos in Time Dependent Variational Approximations to Quantum Dynamics
Dynamical chaos has recently been shown to exist in the Gaussian
approximation in quantum mechanics and in the self-consistent mean field
approach to studying the dynamics of quantum fields. In this study, we first
show that any variational approximation to the dynamics of a quantum system
based on the Dirac action principle leads to a classical Hamiltonian dynamics
for the variational parameters. Since this Hamiltonian is generically nonlinear
and nonintegrable, the dynamics thus generated can be chaotic, in distinction
to the exact quantum evolution. We then restrict attention to a system of two
biquadratically coupled quantum oscillators and study two variational schemes,
the leading order large N (four canonical variables) and Hartree (six canonical
variables) approximations. The chaos seen in the approximate dynamics is an
artifact of the approximations: this is demonstrated by the fact that its onset
occurs on the same characteristic time scale as the breakdown of the
approximations when compared to numerical solutions of the time-dependent
Schrodinger equation.Comment: 10 pages (12 figures), RevTeX (plus macro), uses epsf, minor typos
correcte
START in a five-dimensional conformal domain
In this paper we give a brief review of the pseudo-Riemannian geometry of the
five-dimensional homogeneous space for the conformal group O(4,2). Its topology
is described and its relation to the conformally compactified Minkowski space
is described. Its metric is calculated using a generalized half-space
representation. Compactification via Lie-sphere geometry is outlined. Possible
applications to Jaime Keller's START theory may follow by using its predecessor
- the 5-optics of Yu. B. Rumer. The point of view of Rumer is given extensively
in the last section of the paper.
Keywords. Kaluza,Klein, Rumer, conformal symmetry, hyperbolic space, START,
fifth dimension, action coordinate, 5-opticsComment: Latex, 13 pages, 3 figures, added sections 3.2. Christoffel symbols
and geodesics and 3.3. {\Sigma}- as the space of hyperboloids; accepted for
publication in the special volume of AACA in memory of Prof. Jaime Kelle
Periodic Chaotic Billiards: Quantum-Classical Correspondence in Energy Space
We investigate the properties of eigenstates and local density of states
(LDOS) for a periodic 2D rippled billiard, focusing on their quantum-classical
correspondence in energy representation. To construct the classical
counterparts of LDOS and the structure of eigenstates (SES), the effects of the
boundary are first incorporated (via a canonical transformation) into an
effective potential, rendering the one-particle motion in the 2D rippled
billiard equivalent to that of two-interacting particles in 1D geometry. We
show that classical counterparts of SES and LDOS in the case of strong chaotic
motion reveal quite a good correspondence with the quantum quantities. We also
show that the main features of the SES and LDOS can be explained in terms of
the underlying classical dynamics, in particular of certain periodic orbits. On
the other hand, statistical properties of eigenstates and LDOS turn out to be
different from those prescribed by random matrix theory. We discuss the quantum
effects responsible for the non-ergodic character of the eigenstates and
individual LDOS that seem to be generic for this type of billiards with a large
number of transverse channels.Comment: 13 pages, 18 figure
Multitemporal generalization of the Tangherlini solution
The n-time generalization of the Tangherlini solution [1] is considered. The
equations of geodesics for the metric are integrated. For it is shown
that the naked singularity is absent only for two sets of parameters,
corresponding to the trivial extensions of the Tangherlini solution. The motion
of a relativistic particle in the multitemporal background is considered. This
motion is governed by the gravitational mass tensor. Some generalizations of
the solution, including the multitemporal analogue of the Myers-Perry charged
black hole solution, are obtained.Comment: 14 pages. RGA-CSVR-005/9
Remarks on Shannon's Statistical Inference and the Second Law in Quantum Statistical Mechanics
We comment on a formulation of quantum statistical mechanics, which
incorporates the statistical inference of Shannon.
Our basic idea is to distinguish the dynamical entropy of von Neumann, , in terms of the density matrix ,
and the statistical amount of uncertainty of Shannon, , with in the representation where the total
energy and particle numbers are diagonal. These quantities satisfy the
inequality . We propose to interprete Shannon's statistical inference
as specifying the {\em initial conditions} of the system in terms of . A
definition of macroscopic observables which are characterized by intrinsic time
scales is given, and a quantum mechanical condition on the system, which
ensures equilibrium, is discussed on the basis of time averaging.
An interesting analogy of the change of entroy with the running coupling in
renormalization group is noted. A salient feature of our approach is that the
distinction between statistical aspects and dynamical aspects of quantum
statistical mechanics is very transparent.Comment: 16 pages. Minor refinement in the statements in the previous version.
This version has been published in Journal of Phys. Soc. Jpn. 71 (2002) 6
Using the MitoB method to assess levels of reactive oxygen species in ecological studies of oxidative stress
In recent years evolutionary ecologists have become increasingly interested in the effects of reactive
oxygen species (ROS) on the life-histories of animals. ROS levels have mostly been inferred indirectly
due to the limitations of estimating ROS from in vitro methods. However, measuring ROS (hydrogen
peroxide, H2O2) content in vivo is now possible using the MitoB probe. Here, we extend and refine
the MitoB method to make it suitable for ecological studies of oxidative stress using the brown trout
Salmo trutta as model. The MitoB method allows an evaluation of H2O2 levels in living organisms over
a timescale from hours to days. The method is flexible with regard to the duration of exposure and
initial concentration of the MitoB probe, and there is no transfer of the MitoB probe between fish. H2O2
levels were consistent across subsamples of the same liver but differed between muscle subsamples
and between tissues of the same animal. The MitoB method provides a convenient method for
measuring ROS levels in living animals over a significant period of time. Given its wide range of possible
applications, it opens the opportunity to study the role of ROS in mediating life history trade-offs in
ecological settings
License prices for financially constrained firms
It is often alleged that high auction prices inhibit service deployment. We investigate this claim under the extreme case of financially constrained bidders. If demand is just slightly elastic, auctions maximize consumer surplus if consumer surplus is a convex function of quantity (a common assumption), or if consumer surplus is concave and the proportion of expenditure spent on deployment is greater than one over the elasticity of demand. The latter condition appears to be true for most of the large telecom auctions in the US and Europe. Thus, even if high auction prices inhibit service deployment, auctions appear to be optimal from the consumers’ point of view
Herschelobservations of the W3 GMC (II): clues to the formation of clusters of high-mass stars
The W3 giant molecular cloud is a prime target for investigating the formation of high-mass stars and clusters. This second study of W3 within the HOBYS Key Program provides a comparative analysis of subfields within W3 to further constrain the processes leading to the observed structures and stellar population. Probability density
functions (PDFs) and cumulative mass distributions (CMDs) were created from dust column density maps, quantified as extinction AV. The shape of the PDF, typically represented with a lognormal function at low Av “breaking” to a power-law tail at high Av, is influenced by various processes including turbulence and selfgravity. The breaks can also be identified, often more readily, in the CMDs. The PDF break from lognormal (Av(SF)» 6–10 mag) appears to shift to higher Av by stellar feedback, so that high-mass star-forming regions tend to have higher PDF breaks. A second break at Av> 50 mag traces structures formed or influenced by a dynamic process. Because such a process has been suggested to drive high-mass star formation in W3, this second
break might then identify regions with potential for hosting high-mass stars/clusters. Stellar feedback appears to be a major mechanism driving the local evolution and state of regions within W3. A high initial star formation efficiency in a dense medium could result in a self-enhancing process, leading to more compression and favorable
star formation conditions (e.g., colliding flows), a richer stellar content, and massive stars. This scenario would be compatible with the “convergent constructive feedback” model introduced in our previous Herschel study
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