755 research outputs found
Monte-Carlo Modeling of Non-Gravitational Heating Processes in Galaxy Clusters
We consider non-gravitational heating effects on galaxy clusters on the basis
of the Monte-Carlo modeling of merging trees of dark matter halos combined with
the thermal evolution of gas inside each halo. Under the assumption of
hydrostatic equilibrium and the isothermal gas profiles, our model takes
account of the metallicity evolution, metallicity-dependent cooling of gas,
supernova energy feedback, and heating due to jets of radio galaxies in a
consistent manner. The observed properties of galaxy clusters can be explained
in models with higher non-gravitational heating efficiency than that in the
conventional model. Possibilities include jet heating by the Fanaroff-Riley
Type II radio galaxies, and the enhanced star formation efficiency and/or
supernova energy feedback, especially at high redshifts.Comment: 29 pages, 12 figures. To appear in PASJ, February 25, 200
Reliability of merger tree realizations of dark halos in the Monte-Carlo modeling of galaxy formation
We examine the reliability of the merger trees generated for the Monte-Carlo
modeling of galaxy formation. In particular we focus on the cold gas fraction
predicted from the merger trees with different assumptions on the progenitor
distribution function, the timestep, and the mass resolution. We show that the
cold gas fraction is sensitive to the accuracy of the merger trees at
small-mass scales of progenitors at high redshifts. One can reproduce the
Press-Schechter prediction to a reasonable degree by adopting a fairly large
number of redshift bins, N_{step} ~ 1000 in generating merger trees, which is a
factor of ten larger than the canonical value used in previous literature.Comment: 9 pages, 10 figures. To appear in PASJ, October 25, 200
"Measuring the Cost of Imperfect Information in the Tokyo Housing Market"
The cost of imperfect information is estimated in the real estate market of resale condominiums in central Tokyo by using a new, comprehensive data set of resale condominium transactions. The results suggest a substantial cost. Specifically, if information were perfectly available and marketing time is null, sellers would get benefits of 10.58% based on average interest rate, 31.28% on gross rent and 22.59% on net rent, against imputed rent of their property. Buyers spend 1,042,000 Yen on search activities for one transaction, which would be saved if information were prefect. This cost amounts to be equivalent to 13.2% of buyers' average annual income.
Statistical ensembles for phase coexistence states specified by noncommutative additive observables
Coexisting phases in a phase coexistence state cannot be distinguished by
thermodynamic forces, such as temperature and chemical potential, because the
forces take the same values over all coexisting phases. Therefore, to
investigate a phase coexistence state, it is necessary to employ an ensemble in
which all additive observables that distinguish the coexisting phases have
macroscopically definite values. Although the microcanonical ensemble is
conventionally employed as such an ensemble, it becomes ill-defined when some
of the additive observables do not commute with each other, and a new ensemble
has been craved. We propose a novel class of ensembles such that the additive
observables, which are generally noncommutative, always have macroscopically
definite values even in a first-order phase transition region. Using these
ensembles, we propose a concrete method to construct phase coexistence states
of general quantum systems. Furthermore, these ensembles are convenient for
practical calculations because of good analytic properties. To demonstrate that
our formulation successfully gives phase coexistence states of quantum systems,
we apply it to a two-dimensional system whose coexisting phases are
distinguished by an additive observable (order parameter) that does not commute
with the Hamiltonian. To the author's best knowledge, this is the first work
that obtains phase coexistence states separated by phase interfaces at finite
temperature in such a quantum system
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