73,552 research outputs found
Universal properties in ultracold ion-atom interactions
We present some of the universal properties in ion-atom interaction derived
from a newly formulated quantum-defect theory for type of long-range
interactions. For bound states, we present the universal bound spectrum, namely
the equivalent of the Rydberg formula, for ion-atom systems. For scattering, we
introduce the concept of universal resonance spectrum to give a systematic
understanding of many resonances present in ion-atom scattering. The theory
further provides a method for an accurate spectroscopic determination of the
atomic polarizability. It also suggests the existence of atom-like molecules,
in which multiple atoms orbit around a heavy ion.Comment: 4 pages, 2 figure
Holistic Influence Maximization: Combining Scalability and Efficiency with Opinion-Aware Models
The steady growth of graph data from social networks has resulted in
wide-spread research in finding solutions to the influence maximization
problem. In this paper, we propose a holistic solution to the influence
maximization (IM) problem. (1) We introduce an opinion-cum-interaction (OI)
model that closely mirrors the real-world scenarios. Under the OI model, we
introduce a novel problem of Maximizing the Effective Opinion (MEO) of
influenced users. We prove that the MEO problem is NP-hard and cannot be
approximated within a constant ratio unless P=NP. (2) We propose a heuristic
algorithm OSIM to efficiently solve the MEO problem. To better explain the OSIM
heuristic, we first introduce EaSyIM - the opinion-oblivious version of OSIM, a
scalable algorithm capable of running within practical compute times on
commodity hardware. In addition to serving as a fundamental building block for
OSIM, EaSyIM is capable of addressing the scalability aspect - memory
consumption and running time, of the IM problem as well.
Empirically, our algorithms are capable of maintaining the deviation in the
spread always within 5% of the best known methods in the literature. In
addition, our experiments show that both OSIM and EaSyIM are effective,
efficient, scalable and significantly enhance the ability to analyze real
datasets.Comment: ACM SIGMOD Conference 2016, 18 pages, 29 figure
Towards Anisotropy-Free and Non-Singular Bounce Cosmology with Scale-invariant Perturbations
We investigate non-singular bounce realizations in the framework of
ghost-free generalized Galileon cosmology, which furthermore can be free of the
anisotropy problem. Considering an Ekpyrotic-like potential we can obtain a
total Equation-of-State (EoS) larger than one in the contracting phase, which
is necessary for the evolution to be stable against small anisotropic
fluctuations. Since such a large EoS forbids the Galileon field to generate the
desired form of perturbations, we additionally introduce the curvaton field
which can in general produce the observed nearly scale-invariant spectrum. In
particular, we provide approximate analytical and exact semi-analytical
expressions under which the bouncing scenario is consistent with observations.
Finally, the combined Galileon-curvaton system is free of the Big-Rip after the
bounce.Comment: 13 pages, 9 figure
- …