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Search Results: 1 - 10 of 4712 matches for " Jae Hyung Yee "
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Variational Approach to Quantum Field Theory: Gaussian Approximation and the Perturbative Expansion around It
Jae Hyung Yee
Physics , 1997,
Abstract: The functional Schrodinger picture formulation of quantum field theory and the variational Gaussian approximation method based on the formulation are briefly reviewed. After presenting recent attempts to improve the variational approximation, we introduce a new systematic method based on the background field method, which enables one to compute the order-by-order correction terms to the Gaussian approximation of the effective action.
Vortex Solutions of a Fermion Maxwell-Chern-Simons Theory
Jae Hyung Yee
Physics , 1998,
Abstract: We explain how static multi-vortex solutions arise in non-linear field theories, by taking the non-linear Schr\"odinger equation coupled to Chern-Simons field (Jackiw-Pi model) and a fermion Chern-Simons theory as simple examples. We then construct a fermion Maxwell-Chern-Simons theory which has consistent static field equations, and show that it has the same vortex solutions as the Jackiw-Pi model, but gives rise to quite different vortex dynamics.
Optimized post Gaussian approximation in the background field method
A. Rakhimov,Jae Hyung Yee
Physics , 2002, DOI: 10.1142/S0217751X04017884
Abstract: We have extended the variational perturbative theory based on the back ground field method to include the optimized expansion of Okopinska and the post Gaussian effective potential of Stansu and Stevenson. This new method provides much simpler way to compute the correction terms to the Gausssian effective action (or potential). We have also renormalized the effective potential in 3+1 dimensions by introducing appropriate counter terms in the lagrangian
Unitarity in space-time noncommutative field theories
Chaiho Rim,Jae Hyung Yee
Physics , 2002, DOI: 10.1016/j.physletb.2003.08.073
Abstract: In non-commutative field theories conventional wisdom is that the unitarity is non-compatible with the perturbation analysis when time is involved in the non-commutative coordinates. However, as suggested by Bahns et.al. recently, the root of the problem lies in the improper definition of the time-ordered product. In this article, functional formalism of S-matrix is explicitly constructed for the non-commutative $\phi^p$ scalar field theory using the field equation in the Heisenberg picture and proper definition of time-ordering. This S-matrix is manifestly unitary. Using the free spectral (Wightmann) function as the free field propagator, we demonstrate the perturbation obeys the unitarity, and present the exact two particle scattering amplitude for 1+1 dimensional non-commutative nonlinear Schr\"odinger model.
A new variational perturbation method for double well oscillators
Hyeong-Chan Kim,Jae Hyung Yee
Physics , 2007, DOI: 10.1016/j.aop.2007.11.006
Abstract: We propose a variational perturbation method based on the observation that eigenvalues of each parity sector of both the anharmonic and double-well oscillators are approximately equi-distanced. The generalized deformed algebra satisfied by the invariant operators of the systems provides well defined Hilbert spaces to both of the oscillators. There appears a natural expansion parameter defined by the ratios of three distance scales of the trial wavefunctions. The energies of the ground state and the first order excited state, in the $0^{th}$ order variational approximation, are obtained with errors $<10^{-2}$% for vast range of the coupling strength for both oscillators. An iterative formula is presented which perturbatively generates higher order corrections from the lower order invariant operators and the first order correction is explicitly given.
Non-perturbative approach for the time-dependent symmetry breaking
Hyeong-Chan Kim,Jae Hyung Yee
Physics , 2002, DOI: 10.1103/PhysRevD.69.025003
Abstract: We present a variational method which uses a quartic exponential function as a trial wave-function to describe time-dependent quantum mechanical systems. We introduce a new physical variable $y$ which is appropriate to describe the shape of wave-packet, and calculate the effective action as a function of both the dispersion $\sqrt{< \hat{q}^2>}$ and $y$. The effective potential successfully describes the transition of the system from the false vacuum to the true vacuum. The present method well describes the long time evolution of the wave-function of the system after the symmetry breaking, which is shown in comparison with the direct numerical computations of wave-function.
Perturbative Expansion around the Gaussian Effective Action: The Background Field Method
Geon Hyoung Lee,Jae Hyung Yee
Physics , 1997, DOI: 10.1103/PhysRevD.56.6573
Abstract: We develop a systematic method of the perturbative expansion around the Gaussian effective action based on the background field method. We show, by applying the method to the quantum mechanical anharmonic oscillator problem, that even the first non-trivial correction terms greatly improve the Gaussian approximation.
Liouville-von Neumann approach and time-dependent Gaussian approximation
Hyeong-Chan Kim,Jae Hyung Yee
Physics , 2002,
Abstract: We show that Liouville-von Neumann approach to quantum mechanical systems, which demands the existence of invariant operators, reproduces the time-dependent variational Gaussian approximation. We find the effective action of the time-dependent systems and show that many aspects of the dynamics are independent of the details of time evolution, e.g., the squeezing of the wave-function is determined by the effective potential of the final stage of time-evolution.
Time-dependent driven anharmonic oscillator and the adiabaticity
Hyeong-Chan Kim,Jae Hyung Yee
Physics , 2002, DOI: 10.1103/PhysRevA.66.032117
Abstract: We use the Liouville-von Neumann (LvN) approach to study the dynamics and the adiabaticity of a time-dependent driven anharmonic oscillator as an eample of non-equilibrium quantum dynamics. We show that the adiabaticity is minimally broken in the sense that a gaussian wave-packet at the past infinity evolves to coherent states, however slowly the potential changes, its coherence factor is order of the coupling. We also show that the dynamics are governed by an equation of motion similar to the Kepler motion which satisfies the angular momentum conservation.
Comments on "Entropy of 2D Black Holes from Counting Microstates"
Mu-In Park,Jae Hyung Yee
Physics , 1999, DOI: 10.1103/PhysRevD.61.088501
Abstract: In a recent letter, Cadoni and Mignemi proposed a formulation for the statistical computation of the 2D black holes entropy. We present a criticism about their formulation.
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