3,558 research outputs found
Sampling the Probability Distribution of Type Ia Supernova Lightcurve Parameters in Cosmological Analysis
In order to obtain robust cosmological constraints from Type Ia supernova (SN
Ia) data, we have applied Markov Chain Monte Carlo (MCMC) to SN Ia lightcurve
fitting. We develop a method for sampling the resultant probability density
distributions (pdf) of the SN Ia lightcuve parameters in the MCMC likelihood
analysis to constrain cosmological parameters, and validate it using simulated
data sets. Applying this method to the Joint Lightcurve Analysis (JLA) data set
of SNe Ia, we find that sampling the SN Ia lightcurve parameter pdf's leads to
cosmological parameters closer to that of a flat Universe with a cosmological
constant, compared to the usual practice of using only the best fit values of
the SN Ia lightcurve parameters. Our method will be useful in the use of SN Ia
data for precision cosmology.Comment: 9 pages, 6 figures, 4 tables. Revised version accepted by MNRA
Geometry effects in confined space
In this paper we calculate some exact solutions of the grand partition
functions for quantum gases in confined space, such as ideal gases in two- and
three-dimensional boxes, in tubes, in annular containers, on the lateral
surface of cylinders, and photon gases in three-dimensional boxes. Based on
these exact solutions, which, of course, contain the complete information about
the system, we discuss the geometry effect which is neglected in the
calculation with the thermodynamic limit , and analyze the
validity of the quantum statistical method which can be used to calculate the
geometry effect on ideal quantum gases confined in two-dimensional irregular
containers. We also calculate the grand partition function for phonon gases in
confined space. Finally, we discuss the geometry effects in realistic systems.Comment: Revtex,15 pages, no figur
Do bosons obey Bose-Einstein distribution: two iterated limits of Gentile distribution
It is a common impression that by only setting the maximum occupation number
to infinity, which is the demand of the indistinguishability of bosons, one can
achieve the statistical distribution that bosons obey -- the Bose-Einstein
distribution. In this letter, however, we show that only with an infinite
maximum occupation number one cannot uniquely achieve the Bose-Einstein
distribution, since in the derivation of the Bose-Einstein distribution, the
problem of iterated limit is encountered. For achieving the Bose-Einstein
distribution, one needs to take both the maximum occupation number and the
total number of particles to infinities, and, then, the problem of the order of
taking limits arises. Different orders of the limit operations will lead to
different statistical distributions. For achieving the Bose-Einstein
distribution, besides setting the maximum occupation number, we also need to
state the order of the limit operations.Comment: 6 pages, no figur
Terahertz quantum plasmonics at nanoscales and angstrom scales
Through the manipulation of metallic structures, light-matter interaction can enter into the realm of quantum mechanics. For example, intense terahertz pulses illuminating a metallic nanotip can promote terahertz field-driven electron tunneling to generate enormous electron emission currents in a subpicosecond time scale. By decreasing the dimension of the metallic structures down to the nanoscale and angstrom scale, one can obtain a strong field enhancement of the incoming terahertz field to achieve atomic field strength of the order of V/nm, driving electrons in the metal into tunneling regime by overcoming the potential barrier. Therefore, designing and optimizing the metal structure for high field enhancement are an essential step for studying the quantum phenomena with terahertz light. In this review, we present several types of metallic structures that can enhance the coupling of incoming terahertz pulses with the metals, leading to a strong modification of the potential barriers by the terahertz electric fields. Extreme nonlinear responses are expected, providing opportunities for the terahertz light for the strong light-matter interaction. Starting from a brief review about the terahertz field enhancement on the metallic structures, a few examples including metallic tips, dipole antenna, and metal nanogaps are introduced for boosting the quantum phenomena. The emerging techniques to control the electron tunneling driven by the terahertz pulse have a direct impact on the ultrafast science and on the realization of next-generation quantum devices
- โฆ