Characteristics of Bose-Einstein condensation in an optical lattice

We discuss several possible experimental signatures of the Bose-Einstein condensation (BEC) transition for an ultracold Bose gas in an inhomogeneous optical lattice. Based on the commonly used time-of-flight imaging technique, we show that the momentum-space density profile in the first Brillouin zone, supplemented by the visibility of interference patterns, provides valuable information about the system. In particular, by crossing the BEC transition temperature, the appearance of a clear bimodal structure sets a qualitative and universal signature of this phase transition. Furthermore, the momentum distribution can also be applied to extract the condensate fraction, which may serve as a promising thermometer in such a system.Comment: 12 pages, 13 figures; Revised version with new figures; Phys. Rev. A 77, 043626 (2008

Reduction from Complementary-Label Learning to Probability Estimates

Complementary-Label Learning (CLL) is a weakly-supervised learning problem that aims to learn a multi-class classifier from only complementary labels, which indicate a class to which an instance does not belong. Existing approaches mainly adopt the paradigm of reduction to ordinary classification, which applies specific transformations and surrogate losses to connect CLL back to ordinary classification. Those approaches, however, face several limitations, such as the tendency to overfit or be hooked on deep models. In this paper, we sidestep those limitations with a novel perspective--reduction to probability estimates of complementary classes. We prove that accurate probability estimates of complementary labels lead to good classifiers through a simple decoding step. The proof establishes a reduction framework from CLL to probability estimates. The framework offers explanations of several key CLL approaches as its special cases and allows us to design an improved algorithm that is more robust in noisy environments. The framework also suggests a validation procedure based on the quality of probability estimates, leading to an alternative way to validate models with only complementary labels. The flexible framework opens a wide range of unexplored opportunities in using deep and non-deep models for probability estimates to solve the CLL problem. Empirical experiments further verified the framework's efficacy and robustness in various settings

The Effects of Driving Restrictions on Air Quality: São Paulo, Bogotá, Beijing, and Tianjin

In a typical driving restriction, vehicle use is restricted based on the vehicle’s license plate; one cannot drive vehicles with certain license plate numbers on certain days. Driving restrictions have been used as a method to reduce urban air pollution or traffic congestion because they are easy and inexpensive to implement. We investigate whether driving restrictions introduced in São Paulo, Bogotá, Beijing and Tianjin have improved air quality. Across different versions of the driving restrictions there is no evidence that the overall air quality at different places has been improved. However, several important results show up in this extensive analysis. Temporal shifting of driving is likely to appear when the restrictions are only effective during certain hours of weekdays. Driving restrictions could potentially reduce the extreme concentrations of air pollutants. Driving restrictions can only be expected to alleviate air pollution when implemented with an extended schedule or in an extended region. The effects of the driving restrictions are primarily on the concentrations of CO and PM10.driving restriction, air quality, Environmental Economics and Policy,

Sintering of Fine Oxide Powders: II, Sintering Mechanisms

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65619/1/j.1151-2916.1997.tb02879.x.pd

Reactive Cerium(IV) Oxide Powders by the Homogeneous Precipitation Method

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66445/1/j.1151-2916.1993.tb03942.x.pd

Capacity Pre-Log of Noncoherent SIMO Channels via Hironaka's Theorem

We find the capacity pre-log of a temporally correlated Rayleigh block-fading SIMO channel in the noncoherent setting. It is well known that for block-length L and rank of the channel covariance matrix equal to Q, the capacity pre-log in the SISO case is given by 1-Q/L. Here, Q/L can be interpreted as the pre-log penalty incurred by channel uncertainty. Our main result reveals that, by adding only one receive antenna, this penalty can be reduced to 1/L and can, hence, be made to vanish in the large-L limit, even if Q/L remains constant as L goes to infinity. Intuitively, even though the SISO channels between the transmit antenna and the two receive antennas are statistically independent, the transmit signal induces enough statistical dependence between the corresponding receive signals for the second receive antenna to be able to resolve the uncertainty associated with the first receive antenna's channel and thereby make the overall system appear coherent. The proof of our main theorem is based on a deep result from algebraic geometry known as Hironaka's Theorem on the Resolution of Singularities

Shakura-Sunyaev Disk Can Smoothly Match Advection-Dominated Accretion Flow

We use the standard Runge-Kutta method to solve the set of basic equations describing black hole accretion flows composed of two-temperature plasma. We do not invoke any extra energy transport mechanism such as thermal conduction and do not specify any ad hoc outer boundary condition for the advection-dominated accretion flow (ADAF) solution. We find that in the case of high viscosity and non-zero radiative cooling, the ADAF solution can have an asymptotic approach to the Shakura-Sunyaev disk (SSD) solution, and the SSD-ADAF transition radius is close to the central black hole. Our results further prove the mechanism of thermal instability-triggered SSD-ADAF transition suggested previously by Takeuchi & Mineshige and Gu & Lu.Comment: 10 pages, 2 figures, accepted for publication in ApJ Letter