arXiv subjects

M. -C. Chu

Publications and source records attributed to M. -C. Chu.

49 records · Page 3Linked to original sources

arXiv2001

A dynamical chiral bag model

We study a dynamical chiral bag model, in which massless fermions are confined within an impenetrable but movable bag coupled to meson fields. The self-consistent motion of the bag is obtained by solving the equations of motion exactly assuming spherical symmetry. When the bag interacts with an external meson wave we find three different kinds of resonances: {\it fermionic}, {\it geometric}, and $σ$-resonances. We discuss the phenomenological implications of our results.

nucl-th↗

arXiv2000

Energy focusing inside a dynamical cavity

We study the exact classical solutions for a real scalar field inside a cavity with a wall whose motion is self-consistently determined by the pressure of the field itself. We find that, regardless of the system parameters, the long-time solution always becomes nonadiabatic and the field's energy concentrates into narrow peaks, which we explain by means of a simple mechanical system. We point out implications for the quantized theory.

physics.optics↗

arXiv2000

Motional dressed states in a Bose condensate: Superfluidity at supersonic speed

We present an exact analytic solution of a nonlinear Schrödinger field interacting with a moving potential (obstacle) at supersonic speed. We show that the field forms a stable shape-invariant structure localized around the obstacle --- a dressing effect that protects the field against excitations by the obstacle.

cond-mat.soft↗

arXiv1999

The Schrodinger particle in an oscillating spherical cavity

We study a Schrodinger particle in an infinite spherical well with an oscillating wall. Parametric resonances emerge when the oscillation frequency is equal to the energy difference between two eigenstates of the static cavity. Whereas an analytic calculation based on a two-level system approximation reproduces the numerical results at low driving amplitudes, epsilon, we observe a drastic change of behaviour when epsilon > 0.1, when new resonance states appear bearing no apparent relation to the eigenstates of the static system.

quant-ph↗

arXiv1997

Temperature dependence of instantons in QCD

We investigate the temperature dependence of the instanton contents of gluon fields, using unquenched lattice QCD and the cooling method. The instanton size parameter deduced from the correlation function decreases from 0.44fm below the phase-transition temperature $T_c$ ($\approx 150$MeV) to 0.33fm at 1.3 $T_c$. The instanton charge distribution is Poissonian above $T_c$, but it deviates from the convoluted Poisson at low temperature. The topological susceptibility decreases rapidly below $T_c$, showing the apparent restoration of the $U(1)_A$ symmetry already at $T \approx T_c$.

hep-lat↗

arXiv1994

Instanton content of finite temperature QCD matter

We investigate the temperature dependence of the instanton content of gluon fields and their contribution to quark correlation using quenched lattice QCD and the cooling method. We found a suppression of the topological susceptibility at finite temperature, agreeing with the PCAC expectation at low temperature and enhanced suppression for temperatures at and above the deconfinement transition. For temperatures up to about 334 MeV, the topological charge correlation agrees well with a single instanton profile, though the size parameter seems to change across the phase transition. The screening wave functions for the pion and the rho become slightly more compact at higher temperatures. Lattice cooling shows no contribution from the instantons to the screening wave functions at temperatures above the phase transition.

nucl-th↗

arXiv1994

Pion interferometry with pion-source-medium interactions

An extended pion source, which can be temporarily created by a high energy nuclear collision, will also absorb and distort the outgoing pions. We discuss how this effect alters the interferometric pattern of the two-pion momentum correlation function. In particular, we show that the two-pion correlation function decreases rapidly when the opening angle between the pions increases. The opening-angle dependence should serve as a new means of obtaining information about the pion source in the analysis of experimental data.

nucl-th↗

arXiv1993

Evidence for the Role of Instantons in Hadron Structure from Lattice QCD

Cooling is used as a filter on a set of gluon fields sampling the Wilson action to selectively remove essentially all fluctuations of the gluon field except for the instantons. The close agreement between quenched lattice QCD results with cooled and uncooled configurations for vacuum correlation functions of hadronic currents and for density-density correlation functions in hadronic bound states provides strong evidence for the dominant role of instantons in determining light hadron structure and quark propagation in the QCD vacuum.

hep-lat↗

arXiv1993

Evidence for the Role of Instantons in Hadron Structure from Lattice QCD

hep-lat↗

arXiv1993

Correlation Functions of Hadron Currents in the QCD Vacuum Calculated in Lattice QCD

Point-to-point vacuum correlation functions for spatially separated hadron currents are calculated in quenched lattice QCD on a $16^3\times 24$ lattice with $6/g^2=5.7$. The lattice data are analyzed in terms of dispersion relations, which enable us to extract physical information from small distances where asymptotic freedom is apparent to large distances where the hadronic resonances dominate. In the pseudoscalar, vector, and axial vector channels where experimental data or phenomenological information are available, semi-quantitative agreement is obtained. In the nucleon and delta channels, where no experimental data exist, our lattice data complement experiments. Comparison with approximations based on sum rules and interacting instantons are made, and technical details of the lattice calculation are described.

hep-lat↗

arXiv1992

Lattice Calculation of Point-to-Point Hadron Current Correlation

Point-to-point correlation functions of hadron currents in the QCD vacuum are calculated on a lattice and analyzed using dispersion relations, providing physical information down to small spatial separations. Qualitative agreement with phenomenological results is obtained in channels for which experimental data are available, and these correlation functions are shown to be useful in exploring approximations based on sum rules and interacting instantons.

hep-lat↗

arXiv1992

Lattice Analysis of Two-Point Hadronic Correlators in the QCD Vacuum

Results from the first lattice QCD analysis of vacuum correlators of local hadronic currents using dispersion relations are presented. We have explored the vector, pseudoscalar, axial, and scalar meson channels, and the proton-like and delta-like baryon channels. The lattice results are shown to agree qualitatively with experimental results in channels where experimental data exist, and shed insight into interacting instanton approximations and sum rule calculations in the other channels. 3 figures included (as PostScript files): pi.ps, nd.ps, va.ps : Search for %%% to retrieve the files. Latex file, needs espcrc2.sty (Search for %%%).

hep-lat↗

arXiv1992

Lattice Calculation of QCD Vacuum Correlation Functions

The first exploratory calculations of QCD vacuum correlation functions on a lattice are reported. Qualitative agreement with phenomenological results is obtained in channels for which experimental data are available, and these correlation functions are shown to be useful in exploring approximations based on sum rules and interacting instantons.

hep-lat↗