arXiv subjects

Soo-Young Lee

Publications and source records attributed to Soo-Young Lee.

48 records · Page 3Linked to original sources

arXiv1999

Bifurcation of Periodic Instanton in Decay-Rate Transition

We investigate a bifurcation of periodic instanton in Euclidean action-temperature diagram in quantum mechanical models. It is analytically shown that multiple zero modes of fluctuation operator should be arised at bifurcation points. This fact is used to derive a condition for the appearance of bifurcation points in action-temperature diagram. This condition enables one to compute the number of bifurcation points for a given quantum mechanical system and hence, to understand the whole behaviour of decay rate. It is explicitly shown that the previous criterion derived by nonlinear perturbation or negative-mode consideration is special limit of our case.

hep-th↗

arXiv1999

Oscillation of the tunnel splitting in nanospin systems within the particle mapping formalism

The oscillation of tunnel splitting in the biaxial spin system within magnetic field along the anisotropy axis is analyzed within the particle mapping approach, rather than in the (θ-ϕ) spin coherent-state representation. In our mapping procedure, the spin system is transformed into a particle moving in the restricted $S^1$ geometry whose wave function subjects to the boundary condition involving additional phase shift. We obtain the new topological phase that plays the same role as the Wess-Zumino action in spin coherent-state representation. Considering the interference of two possible trajectories, instanton and anti-instanton, we get the identical condition for the field at which tunneling is quenched, with the previous result within spin coherent-state representation.

cond-mat.mes-hall↗

arXiv1999

Winding Number Transition at Finite Temperature : Mottola-Wipf model with and without Skyrme term

The winding number transition in the Mottola-Wipf model with and without Skyrme term is examined. For the model with Skyrme term the number of discrete modes of the fluctuation operator around sphaleron is shown to be dependent on the value of $λm^2$. Following Gorokhov and Blatter we derive a sufficient condition for the sharp first-order transition, which indicates that first-order transition occurs when $0< λm^2 < 0.0399$ and $2.148 < λm^2$. In the intermediate region of $λm^2$ the winding number transition is conjectured to be smooth second order. For the model without Skyrme term the winding number transition is always first order regardless of the value of parameter.

hep-th↗

arXiv1999

Spatial Compactification and Decay-Rate Behavior

The pahse transition from instanton-dominated quantum tunneling regime to sphaleron-dominated classical crossover regime is explored in (1+1)-dimensional scalar field theory when spatial coordinate is compactified. It is shown that the type of sphaleron transition is critically dependent on the circumference of the spatial coordinate.

hep-th↗

arXiv1999

Critical value of symmetry breaking parameter in the phase transition of decay rate

Phase transition of decay rate from quantum tunneling to thermal activity regimes is investigated in (3+1)-dimensional field theories with symmetry breaking term $fϕ$. By applying the two independent criteria for the sharp first-order transition to the same model, the upper and lower bounds of critical value of the symmetry breaking parameter are obtained. Unlike two dimensional case continuum states of the fluctuation operator near sphaleron solution play an important role to determine the type of transition.

hep-th↗

arXiv1999

Negative modes and decay-rate transition

We investigate a relationship between the number of the negative modes around periodic instanton solution and the type of the decay-rate transition. It is shown that for the case of first-order decay-rate transition the lowest positive mode at low energy periodic instanton becomes additional negative mode at high energy regime, while in the second-order case there is only one negative mode in the full range of energy. This kind of analysis on the negative modes makes it possible to derive the criterion for the first-order transition.

hep-th↗

arXiv1998

Correspondence between classical dynamics and energy level spacing distribution in the transition billiard systems

The Robnik billiard is investigated in detail both classically and quantally in the transition range from integrable to almost chaotic system. We find out that a remarkable correspondence between characteristic features of classical dynamics, especially topological structure of integrable regions in the Poincaré surface of section, and the statistics of energy level spacings appears with a system parameter $λ$ being varied. It is shown that the variance of the level spacing distribution changes its behavior at every particular values of $λ$ in such a way that classical dynamics changes its topological structure in the Poincaré surface of section, while the skewness and the excess of the level spacings seem to be closely relevant to the interface structure between integrable region and chaotic sea rather than inner structure of intergrable regoin.

chao-dyn↗

arXiv1998

Transitions to quantum chaos in a generic one-parameter family of billiards

Generic one-parameter billiards are studied both classically and quantally. The classical dynamics for the billiards makes a transition from regular to fully chaotic motion through intermediary soft chaotic system. The energy spectra of the billiards are computed using finite element method which has not been applied to the euclidean billiard. True generic quantum chaotic transitional behavior and its sensitive dependence on classical dynamics are uncovered for the first time. That is, this sensitive dependence of quantum spectral measures on classical dynamics is a genuine manifestation of quantum chaos.

chao-dyn↗

arXiv1997

Propagator for an Aharonov-Bohm-Coulomb system

The propagator of three-dimensional Aharonov-Bohm-Coulomb system is calculated by following the Duru-Kleinert method. It is shown that the system is reduced to two independent two dimensional Aharonov-Bohm plus harmonic oscillator systems through dimensional extension and Kustaanheimo-Stiefel transformation. The energy spectrum is deduced.

quant-ph↗

arXiv1996

Test of dilute gas approximation in quantum mechanical model

The validity of dilute gas approximation is explored by making use of the large-sized instanton in quantum mechanical model. It is shown that the Euclidean probability amplitude derived through a dilute gas approximation not only cannot explain the result of the linear combination of atomic orbitals approximation, but also does not exhibit a proper limiting case when the size of instanton is very large.

hep-th↗

arXiv1996

Effect of Anharmonicity on the WKB Energy Splitting in a Double Well Potential

We investigate the effect of anharmonicity on the WKB approximation in a double well potential. By incorporating the anharmonic perturbation into the WKB energy splitting formula we show that the WKB approximation can be greatly improved in the region over which the tunneling is appreciable. We also observe that the usual WKB results can be obtained from our formalism as a limiting case in which the two potential minima are far apart.

quant-ph↗

arXiv1996

Instantonic approach to triple well potential

By using a usual instanton method we obtain the energy splitting due to quantum tunneling through the triple well barrier. It is shown that the term related to the midpoint of the energy splitting in propagator is quite different from that of double well case, in that it is proportional to the algebraic average of the frequencies of the left and central wells.

quant-ph↗