New Results from the Daya Bay Reactor Neutrino Experiment

This presentation describes a precision result of the neutrino mixing parameter, $\sin^2 2\theta_{13}$, and the first direct measurement of the antineutrino mass-squared difference $\sin^2(\Delta_{ee}) \equiv \cos^2 \theta_{12} \sin^2 \Delta_{31} + \sin^2 \theta_{12} \sin^2 \Delta_{32}$ from the Daya Bay Reactor Neutrino Experiment. The above results are based on the six detector data-taking from 24 December 2011 to 28 July 2012. By using the observed antineutrino rate and the energy spectrum analysis, the results are $\sin^2 2\theta_{13}=0.090^{+0.008}_{-0.009}$ and $| \Delta m^2_{ee}| = 2.59^{+0.19}_{-0.20} \cdot 10^{-3}$eV$^2$ with a $\chi^2$/NDF of 162.7/153. The value of $| \Delta m^2_{ee}|$ is consistent with $| \Delta m^2_{\mu\mu}|$ measured in muon neutrino beam experiments.Comment: to appear in the proceedings of The 10th International Symposium on Cosmology and Particle Astrophysics (CosPA2013

Infrared Behavior of Quantum Fields in Inflationary Cosmology -- Issues and Approaches: an overview

This is a pedagogical guide to works on this subject which began in the 80s but has seen vibrant activities in the last decade. It aims to help orient readers, especially students, who wish to enter into research but bewildered by the vast and diverse literature on this subject. We describe the three main veins of activities: the Euclidean zero-mode dominance, the Lorentzian interacting quantum field theory and the classical stochastic field theory approaches in some detail, explaining the underlying physics and the technicalities of each. We show how these approaches are interconnected, and highlight recent papers which contain germs of worthy directions for future developments.Comment: 56 pages, a chapter in the forthcoming book "Semiclassical and Stochastic Gravity -- Quantum Field Effects on Curved Spacetime" by Bei-Lok B. Hu and Enric Verdaguer, Cambridge University Press 2019. arXiv admin note: text overlap with arXiv:1807.05964, arXiv:1506.06183, arXiv:1412.4893, arXiv:1808.00338, arXiv:1603.07338, arXiv:1402.2076, arXiv:1310.0367, arXiv:1212.3058, arXiv:0807.5006, arXiv:1205.3097 by other author

Recent Results from Daya Bay Reactor Neutrino Experiment

The Daya Bay reactor neutrino experiment announced the discovery of a non-zero value of \sin^22\theta_{13} with significance better than 5 \sigma in 2012. The experiment is continuing to improve the precision of \sin^22\theta_{13} and explore other physics topics. In this talk, I will show the current oscillation and mass-squared difference results which are based on the combined analysis of the measured rates and energy spectra of antineutrino events, an independent measurement of \theta_{13} using IBD events where delayed neutrons are captured on hydrogens, and a search for light sterile neutrinos.Comment: this proceedings is for the Moriond 2015 EW sessio

BEC Collapse, Particle Production and Squeezing of the Vacuum

Phenomena associated with the controlled collapse of a Bose-Einstein condensate described in the experiment of Donley et al (E. Donley et. al., Nature 412, 295 (2001); N. Claussen, Ph. D. Thesis, U. of Colorado (2003)) are explained here as a consequence of the squeezing and amplification of quantum fluctuations above the condensate by the condensate dynamics. In analyzing the changing amplitude and particle contents of these excitations, our simple physical picture provides excellent quantitative fits with experimental data on the scaling behavior of the collapse time and the amount of particles emitted in the jets.Comment: 4 pages, 3 figure

Gauge-invariant Effective Action for the Dynamics of Bose-Einstein condensates with a fixed number of atoms

In this paper we present a particle-number-conserving (PNC) functional formalism to describe the dynamics of a cold bosonic gas. Treating the total number of particles as a constraint, whereby the phase invariance of the theory becomes local in time, we study this U(1) gauge theory using DeWitt's "gauge invariant effective action" techniques. Our functional formulation and earlier PNC proposals are shown to yield equivalent results to next-to-leading order in an expansion in the inverse powers of the total number of particles. In this more general framework we also show that earlier PNC proposals can be seen as different gauge (and gauge fixing condition) choices within the same physical theory.Comment: 25 page

Equivalence Principle for Quantum Systems: Dephasing and Phase Shift of Free-Falling Particles

We ask the question how the (weak) equivalence principle established in classical gravitational physics should be reformulated and interpreted for massive quantum objects that may also have internal degrees of freedom (dof). This inquiry is necessary because even elementary concepts like a classical trajectory are not well defined in quantum physics -- trajectories originating from quantum histories become viable entities only under stringent decoherence conditions. From this investigation we posit two logically and operationally distinct statements of the equivalence principle for quantum systems: Version A: The probability distribution of position for a free-falling particle is the same as the probability distribution of a free particle, modulo a mass-independent shift of its mean. Version B: Any two particles with the same velocity wave-function behave identically in free fall, irrespective of their masses. Both statements apply to all quantum states, including non-classical ones, and also for composite particles with quantum internal dof. We also investigate the consequences of the interaction between internal and external dof induced by free fall. For a class of initial states, we find a dephasing for the translational dof, namely, the suppression of the off-diagonal terms of the density matrix, in the position basis. We also find a gravitational phase shift in the reduced density matrix of the internal dof that does not depend on the particle's mass. For classical states, the phase shift has a natural classical interpretation in terms of gravitational red-shift and special relativistic time-dilation.Comment: 23 pages, small changes, explanations added, to appear in CQ

Quantum Noise in Gravitation and Cosmology

We begin by enumerating the many processes in gravitation and cosmology where quantum noise and fluctuations play an active role such as particle creation, galaxy formation and entropy generation. Using the influence functional we first explain the origin and nature of noise in quantum systems interacting with an environment at a finite temperature. With linear coupling to nonohmic baths or at low temperatures, colored noise and nonlocal dissipation would appear and for nonlinear coupling multiplicative noise is generally expected. We derive a generalized fluctuation- dissipation relation for these systems. Then using a model of quantum Brownian motion in a bath of parametric oscillators, we show how noise and dissipation can be related to the Bogolubov coefficients of parametric amplification, which in the second-quantized sense, depicts cosmological particle creation in a dynamic background. We then calculate the influence functional and study the noise characteristics of quantum fields as probed by a particle detector. As examples, we show that an uniformly- accelerated observer in flat space or an inertial observer in an exponentially expanding (de Sitter) universe would see a thermal particle spectrum, recovering the well-known results of Unruh and Gibbons and Hawking , as inspired by the Hawking effect in black holes. We show how this method can be effectively used for treating the backreaction of particle creation and other quantum field processes on theComment: Latex 25 pages. Invited talk delivered by B. L. Hu at the Workshop on Noise and Order, Los Alamos National Laboratory, September, 199

Probing a Gravitational Cat State

We investigate the nature of a gravitational two-state system (G2S) in the simplest setup in Newtonian gravity. In a quantum description of matter a single motionless massive particle can in principle be in a superposition state of two spatially-separated locations. This superposition state in gravity, or gravitational cat state, would lead to fluctuations in the Newtonian force exerted on a nearby test particle. The central quantity of importance for this inquiry is the energy density correlation. This corresponds to the noise kernel in stochastic gravity theory, evaluated in the weak field nonrelativistic limit. In this limit, quantum fluctuations of the stress energy tensor manifest as the fluctuations of the Newtonian force. We describe the properties of such a G2S system and present two ways of measuring the cat state for the Newtonian force, one by way of a classical probe, the other a quantum harmonic oscillator. Our findings include: (i) mass density fluctuations persist even in single particle systems, and they are of the same order of magnitude as the mean; (ii) a classical probe generically records a non-Markovian fluctuating force; (iii) a quantum probe interacting with the G2S system may undergo Rabi oscillations in a strong coupling regime. This simple prototypical gravitational quantum system could provide a robust testing ground to compare predictions from alternative quantum theories, since the results reported here are based on standard quantum mechanics and classical gravity.Comment: 25 pages, 1 figur

New analytical methods for gravitational radiation and reaction in binaries with arbitrary mass ratio and relative velocity

We present a new analytical framework for describing the dynamics of a gravitational binary system with unequal masses moving with arbitrary relative velocity, taking into account the backreaction from both compact objects in the form of tidal deformation, gravitational waves and self forces. Allowing all dynamical variables to interact with each other in a self-consistent manner this formalism ensures that all the dynamical quantities involved are conserved on the background spacetime and obey the gauge invariance under general coordinate transformations that preserve the background geometry. Because it is based on a generalized perturbation theory and the important new emphasis is on the self-consistency of all the dynamical variables involved we call it a gravitational perturbation theory with self-consistent backreaction (GP-SCB). As an illustration of how this formalism is implemented we construct perturbatively a self-consistent set of equations of motion for an inspiraling gravitational binary, which does not require extra assumptions such as slow motion, weak-field or small mass ratio for its formulation. This case should encompass the inspiral and possibly the plunge and merger phases of binaries with otherwise general parameters (e.g., mass ratio and relative velocity) though more investigation is needed to substantiate it. In the second part, we discuss how the mass ratio can be treated as a perturbation parameter in the post-Newtonian effective field theory (PN-EFT) approach, thus extending the work of Goldberger and Rothstein for equal mass binaries to variable mass ratios. We provide rough estimates for the higher post-Newtonian orders needed to determine the number of gravitational wave cycles, with a specified precision, that fall into a detector's bandwidth.Comment: 17 pages, 3 figures, Invited contribution to the International Conference on Classical and Quantum Relativistic Dynamics of Particles and Fields (IARD) held at the Aristotle University, Thessaloniki, Greece, 22-26 June 2008. Proceedings to appear in Foundations of Physic

Analysis of a Mathematical Model of Ischemic Cutaneous wounds

Chronic wounds represent a major public health problem affecting 6.5 million people in the United States. Ischemia represents a serious complicating factor in wound healing. In this paper we analyze a recently developed mathematical model of ischemic dermal wounds. The model consists of a coupled system of partial differential equations in the partially healed region, with the wound boundary as a free boundary. The extracellular matrix (ECM) is assumed to be viscoelastic, and the free boundary moves with the velocity of the ECM at the boundary of the open wound. The model equations involve the concentrations of oxygen, cytokines, and the densities of several types of cells. The ischemic level is represented by a parameter which appears in the boundary conditions, 0 <= gamma < 1; gamma near 1 corresponds to extreme ischemia and gamma = 0 corresponds to normal non-ischemic conditions. We establish global existence and uniqueness of the free boundary problem and study the dependence of the free boundary on gamma