arXiv subjects

Hungsoo Kim

Publications and source records attributed to Hungsoo Kim.

28 records · Page 2Linked to original sources

arXiv2002

Singular Quantum Mechanical Viewpoint of Localized Gravity in Brane-World Scenario

The graviton localized on the 3-brane is examined in Randall-Sundrum brane-world scenario from the viewpoint of one-dimensional singular quantum mechanics. For the Randall-Sundrum single brane scenario the one-parameter family of the fixed-energy amplitude is explicitly computed where the free parameter $ξ$ parametrizes the various boundary conditions at the brane. The general criterion for the localized graviton to be massless is derived when $ξ$ is arbitrary but non-zero. When $ξ=0$, the massless graviton is obtained via a coupling constant renormalization. For the two branes picture the fixed-energy amplitude is in general dependent on the two free parameters. The numerical test indicates that there is no massless graviton in this picture. For the positive-tension brane, however, the localized graviton becomes massless when the distance between branes are infinitely large, which is essentially identical to the single brane picture. For the negative-tension brane there is no massless graviton regardless of the distance between branes and choice of boundary conditions.

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arXiv2002

Nonvanishing Cosmological Constant of Flat Universe in Brane-World Scenario

The finite temperature effect is examined in Randall-Sundrum brane-world scenario with inclusion of the matter fields on the brane. At zero temperature it is found that the theory on the brane is conformally invariant, which guarantees $AdS$/CFT. At 4d effective action we derived a temperature-dependent nonvanishing cosmological constant at the flat spacetime limit of brane worldvolume. At the cosmological temperature $3 {\bf K}$ the cosmological constant is roughly $(0.0004 eV)^4$ which is within the upper bound of the recent experimental value $(0.01 eV)^4$

hep-th↗

arXiv2001

Randall-Sundrum Scenario at Nonzero Temperature

The effect of temperature is investigated in the Randall-Sundrum brane-world scenario. It is shown that for a spacetime ansatz motivated by similarity with AdS/CFT correspondence several features of the model, such as its $Z_2$ symmetry, are not maintained at nonzero temperatures.

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arXiv2001

Gross-Ooguri Phase Transition at Zero and Finite Temperature: Two Circular Wilson Loop Case

In the context of $AdS/CFT$ correspondence the two Wilson loop correlator is examined at both zero and finite temperatures. On the basis of an entirely analytical approach we have found for Nambu-Goto strings the functional relation $d S_c^{(Reg)} / dL = 2 πk$ between Euclidean action $S_c$ and loop separation $L$ with integration constant $k$, which corresponds to the analogous formula for point-particles. The physical implications of this relation are explored in particular for the Gross-Ooguri phase transition at finite temperature.

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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.

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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.

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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.

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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.

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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.

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arXiv1998

Effect of dissipation on the decay-rate phase transition

A general condition for sharp transition of decay rate from quantum to thermal regimes is derived in dissipative tunneling models when position dependent mass is involved. It is shown that the effect of dissipation in general changes the order of the phase transition. Especially, for the models with constant mass the Ohmic dissipation enlarges the range of parameters for first-order phase transitions. In the case of second-order phase transition the Ohmic dissipation suppresses the decay rate near the transition temperature(T_c). For the super-Ohmic case the dissipation yields an opposite effects to the Ohmic dissipation within exponential approximation.

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