39,349 research outputs found
Radiation reaction of classical hyperbolic oscillator: experimental signatures
When accelerated by a constant force in the lab frame, a classical charge
experiences no self force. In this case, the particle radiates without
dissipating its kinetic and potential energy. But what happens when the
particle enters another region with equal and opposite acceleration? Does the
oscillating charge lose its mechanical energy similar to a radiating dipole,
even though it seems to lose no mechanical energy within each region of
constant acceleration? In this paper, I will show how mechanical energy is
transferred to radiation energy via the Schott energy when the particle crosses
the boundary between the two regions. In particular, I will show how
preacceleration, which is usually regarded as an unphysical effect of the
Lorentz-Abraham-Dirac self force, is essential for the energy transfer.
Moreover, I will show that the commonly adopted Landau-Lifshitz approximation,
which removes preacceleration, introduces second-order secular energy error. On
a more fundamental level, the validity of classical electrodynamics is in fact
questionable because quantum effects are likely important. The classical
prediction can be tested experimentally by observing frequency chirping of
radiation, whereby micro physics leaves signatures on macroscopic scales. The
required experimental accuracy is estimated. Trap experiment of this type is
complementary to collider experiments that endeavor to observe radiation
reaction for elementary particles.Comment: 42 pages, 8 figures. LLNL-JRNL-76463
Unitarity of exclusive quark combination model: Exotic hadron production, entropy change and charmonium production for colour-singlet many-quark system
Confinement indicates an asymptotic quark state not observable except its
energy is zero. Unitarity indicates that the total probability of a definite
state of quark system to transit to any final state is exactly one. This talk
reviews some important conclusions/predictions from the basic properties like
unitarity of the combination model, as addressed by the title.
We also in the Postscript section address the bottom quark energy loss. In
the discussions around the dinner table in the Rencontre, the author combined
the large transverse momentum J/Psi suppression and the contribution to J/Psi
by B decay in large transverse momentum, made the expectation that bottom quark
energy loss could be quite similar as light quark for b quark transverse
momentum enough larger than b quark mass. This refers to the physical picture
of the jet-medium interaction introduced in la Rencontre de l'annee derniere.Comment: Prepared for the Proceedings of la 46th Rencontre de Moriond, QCD
Sessio
Combination of Heavy Quark with Partons from Quark-Gluon Matter: a Scaling Probe
In relativistic heavy ion collisions, the cross section of heavy hadron
production via the combination of a heavy quark with a light one from the
quark-gluon matter can be factorized. It is the convolution of twist-4
combination matrix elements, the parameters corresponding to the parton
distributions of the quark-gluon matter, as well as the hard partonic cross
section of heavy quark production calculable in PQCD. These parton
distributions and combination matrix elements are functions of a scaling
variable which is the momentum fraction of the heavy quark w.r.t. the heavy
hadron. In the same factorization framework, the combination matrix elements
appear in other `simpler' processes and can be extracted. Taking them as
inputs, comparing with data from RHIC and (future) LHC, we can get the parton
distributions of the quark-gluon matter just as the similar way we get those of
nucleon, pion, or photon, etc..Comment: 17 pages in A4 preprint form and 12pt, 2 figure
Pionization and Energy Loss
This is a version submitted to proceedings of sqm09. The space time of hard
interaction induced radiation (collinear, double log) and
jet-QGM-interaction-induced radiation (bremsstrahlung + pionization) is more
clarified. A hand-drawing picture is attached for interested reader. To measure
y=1.2 to 2.2 more suppressed (than y=0) open charm pT spectrum is predicted and
suggested as a good test.Comment: revtex4 (V5
Exponential Decay of the lengths of Spectral Gaps for Extended Harper's Model with Liouvillean Frequency
In this paper, we study the non-self dual extended Harper's model with
Liouvillean frequency. By establishing quantitative reducibility results
together with the averaging method, we prove that the lengths of spectral gaps
decay exponentially.Comment: A revised version with 1 figur
A Dynamic Programming Implemented 2x2 non-cooperative Game Theory Model for ESS Analysis
Game Theory has been frequently applied in biological research since 1970s.
While the key idea of Game Theory is Nash Equilibrium, it is critical to
understand and figure out the payoff matrix in order to calculate Nash
Equilibrium. In this paper we present a dynamic programming implemented method
to compute 2x2 non-cooperative finite resource allocation game's payoff matrix.
We assume in one population there exists two types of individuals, aggressive
and non-aggressive and each individual has equal and finite resource. The
strength of individual could be described by a function of resource consumption
in discrete development stages. Each individual undergoes logistic growth hence
we divide the development into three stages: initialization, quasilinear growth
and termination. We first discuss the theoretical frame of how to dynamic
programming to calculate payoff matrix then give three numerical examples
representing three different types of aggressive individuals and calculate the
payoff matrix for each of them respectively. Based on the numerical payoff
matrix we further investigate the evolutionary stable strategies (ESS) of the
games.Comment: 9 pages 3 sub models to illustrate how dynamic programming is
implemented to construct payoff matrix of 2x2 symmetric gam
Information-Theoretical Learning of Discriminative Clusters for Unsupervised Domain Adaptation
We study the problem of unsupervised domain adaptation, which aims to adapt
classifiers trained on a labeled source domain to an unlabeled target domain.
Many existing approaches first learn domain-invariant features and then
construct classifiers with them. We propose a novel approach that jointly learn
the both. Specifically, while the method identifies a feature space where data
in the source and the target domains are similarly distributed, it also learns
the feature space discriminatively, optimizing an information-theoretic metric
as an proxy to the expected misclassification error on the target domain. We
show how this optimization can be effectively carried out with simple
gradient-based methods and how hyperparameters can be cross-validated without
demanding any labeled data from the target domain. Empirical studies on
benchmark tasks of object recognition and sentiment analysis validated our
modeling assumptions and demonstrated significant improvement of our method
over competing ones in classification accuracies.Comment: Appears in Proceedings of the 29th International Conference on
Machine Learning (ICML 2012
Controlling azimuthal spoke modes in cylindrical Hall thruster using a segmented anode
Azimuthal spoke-like modes commonly occur in ExB discharges. The natural
occurrence of the spoke mode is correlated with changes of plasma parameters.
Here, instead of allowing these changes to occur naturally, we report a
technique for actively controlling the spoke by adjusting the boundary
condition at the anode. The technique is demonstrated using a cylindrical Hall
thruster equipped with a segmented anode. By varying the voltage and the
relative phases of the anode segments, properties of the azimuthal mode can be
altered substantially, as shown by fast camera images and probe diagnostics.
This technique may be extended to other Hall discharges in order to either
induce or suppress azimuthal activities, and thereby controlling the operation
and the performance of the devices
Large production rate of new and states in high energy multi-production process
The production rate of the X(5568) observed by D0 collabotation is quite
large and can not be understood by various general hadronization mechanism. We
propose an inclusive resonance production formulation to calculate the cross
section and extract the value of the effective wave function at origin. Based
on these results we suspect X() can be copiously produced and
observable at high enenrgy scatterings (the relative production ratio to D_s is
larger than 10 %).
In the updated version the discussions on cluster model and FI are added.
Both cases can not give large rate.
Then we show that pion in X(5568) decay can only gain a very small momentum.
In the pseudo-rapidity region [2,5], large part of the signal pions will be
dismissed by the detector since the transverse mometum is too small and/or
total momentum too small. If further requirement on pion tranverse mometum
larger than 1GeV/c added, almost all signal pions are rejected. But for the
charm partner, this problem does not exist since the charm partner can give a
larger boost factor. A 3D distribution of signal pions are addedComment: 10 pages, 2 figure
Decay Constants of Pseudoscalar Mesons in Bethe-Salpeter Framework with Generalized Structure of Hadron-Quark Vertex
We employ the framework of Bethe-Salpeter equation under Covariant
Instantaneous Ansatz to study the leptonic decays of pseudoscalar mesons. The
Dirac structure of hadron-quark vertex function is generalized to
include various Dirac covariants besides from their complete set.
The covariants are incorporated in accordance with a power counting rule, order
by order in powers of the inverse of the meson mass. The decay constants are
calculated with the incorporation of leading order covariants. Most of the
results are dramatically improved.Comment: new version of the pape
- …