arXiv subjects

Jae-Kwan Kim

Publications and source records attributed to Jae-Kwan Kim.

4 recordsLinked to original sources

arXiv1997

Radiation from a uniformly accelerating harmonic oscillator

We consider a radiation from a uniformly accelerating harmonic oscillator whose minimal coupling to the scalar field changes suddenly. The exact time evolutions of the quantum operators are given in terms of a classical solution of a forced harmonic oscillator. After the jumping of the coupling constant there occurs a fast absorption of energy into the oscillator, and then a slow emission follows. Here the absorbed energy is independent of the acceleration and proportional to the log of a high momentum cutoff of the field. The emitted energy depends on the acceleration and also proportional to the log of the cutoff. Especially, if the coupling is comparable to the natural frequency of the detector ($e^2/(4m) \sim ω_0$) enormous energies are radiated away from the oscillator.

gr-qc↗

arXiv1994

Derivation of the Classical Lagrangian for the Relativistic Spinning Particle

The `classical' model for a massive spinning particle, which was recently proposed, is derived from the isotropic rotator model. Through this derivation, we note that the spin can be understood as the relativistic extension of the isotropic rotator. Furthermore, the variables $t_\m$ corresponding to the $\p^*$ of the `pseudo-classical' model, are necessary for the covariant formulation. The dynamical term for these extra variables is naturally obtained and the meaning of the constraint term $p^\sŁ_{\s\n}+mt_\n =0$, which was recently shown to give `quasi-supersymmetry', is clarified.

hep-th↗

arXiv1994

A Covariant Formulation of Classical Spinning Particle

Covariantly we reformulate the description of a spinning particle in terms of the Poincaré group. We also construct a Lagrangian which entails all possible constraints explicitly; all constraints can be obtained just from the Lagrangian. Furthermore, in this covariant reformulation, the Lorentz element is to be considered to evolve the momentum or spin component from an arbitrary fixed frame and not just from the particle rest frame. In distinction with the usual formulation, our system is directly comparable with the pseudo-classical formulation. We get a peculiar symmetry which resembles the supersymmetry of the pseudo-classical formulation.

hep-th↗

arXiv1993

Relation between Classical and Pseudo-classical Spinning Particle

The spin degrees of freedom for the relativistic particle are described by either Poincaré group variables (classically) or Grassmann variables (pseudo-classically). The relationship between those two descriptions are given. In doing that, appropriate constraints are constructed to put into the lagrangian. Especially a natural relation of Poincaré group variables and Grassmann variables is obtained. Hopf fibration relating the spin momentum to the group is just the right transformation of the spin momentum under Poincaré group. And with the relation just mentioned, pseudoclassical lagrangian is derived naturally from the classical one.

hep-th↗