Publications (11)38.68 Total impact

 [Show abstract] [Hide abstract]
ABSTRACT: Speckle tracking is widely used for elastography in ultrasound imaging. Traditional speckle tracking algorithms accurately detect axial motion, but have difficulty detecting lateral motion, even with a significant computational burden. A modified cross correlation algorithm with a synthetic lateral phase has been developed to reduce the computation time, allowing for realtime implementation. The modified algorithm yields results comparable to those of existing lateral displacement tracking methods. With the modified method, lateral movement in the micrometer range can be successfully tracked while reducing computational time by more than a factor of two. This algorithm will serve as a useful tool to further advance ultrasound elastography.  [Show abstract] [Hide abstract]
ABSTRACT: We study the holographic QCD in the hadronic medium by using the soft wall model. We discuss the HawkingPage transition between ReissnerNordstr\"{o}m AdS black hole and thermal charged AdS of which the geometries correspond to deconfinement and confinement phases respectively. We also present the numerical result of the vector and axial vector meson spectra depending on the quark density.  [Show abstract] [Hide abstract]
ABSTRACT: It is beyond the present techniques based on perturbation theory to reveal the nature of phase transitions in strongly interacting field theories. Recently, the holographic approach has provided us with an effective dual description, mapping strongly coupled conformal field theories to classical gravity theories. Resorting to the holographic superconductor model, we propose a general criterion for the nature of the superconducting phase transition based on effective interactions between vortices. We find "tricritical" points in terms of the chemical potential for U(1) charges and an effective GinzburgLandau parameter, where vortices do not interact to separate the second order (repulsive) from the first order (attractive) transitions. We interpret the first order transition as the ColemanWeinberg mechanism, arguing that it is relevant to superconducting instabilities around quantum criticality.  [Show abstract] [Hide abstract]
ABSTRACT: Based on Sen's entropy function formalism, we consider the Bekenstein–Hawking entropy of the extremal Kerr(anti)de Sitter black holes in 4dimensions. Unlike the extremal Kerr black hole case with flat asymptotic geometry, where the Bekenstein–Hawking entropy S is proportional to the angular momentum J, we get a quartic algebraic relation between S and J by using the known solution to the Einstein equation. We recover the same relation in the entropy function formalism. Instead of full geometry, we write down an ansatz for the near horizon geometry only. The exact form of the unknown functions and parameters in the ansatz are obtained by solving the differential equations which extremize the entropy function. The results agree with the nontrivial relation between S and J.We also study the Gauss–Bonnet correction to the entropy exploiting the entropy function formalism. We show that the term, though being topological thus does not affect the solution, contributes a constant addition to the entropy because the term shifts the Hamiltonian by that amount.  [Show abstract] [Hide abstract]
ABSTRACT: We study a selfbound dense object in the hard wall model. We consider a spherically symmetric dense object which is characterized by its radial density distribution and nonuniform but spherically symmetric chiral condensate. For this we analytically solve the partial differential equations in the hard wall model and read off the radial coordinate dependence of the density and chiral condensate according to the AdS/CFT correspondence. We then attempt to describe nucleon density profiles of a few nuclei within our framework and observe that the confinement scale changes from a free nucleon to a nucleus. We briefly discuss how to include the effect of higher dimensional operator into our study. We finally comment on possible extensions of our work. Comment: 17 pages, 5 figures, figures replaced, minor revision, to appear in JHEP  [Show abstract] [Hide abstract]
ABSTRACT: In this paper we propose a way of determining the subleading corrections to the BekensteinHawking black hole entropy by considering a modified generalized uncertainty principle with two parameters. In the context of modified generalized uncertainty principle, coefficients of the correction terms of black hole entropy are written in terms of combination of the parameters. We also obtained the corrections to the StefanBoltzman law and the black hole evaporation in terms of the parameters. By estimating those parameters, say by experiment, one can test results from other context of quantum gravity theories such as black hole entropy. KeywordsGeneralized uncertainty principleBlack hole thermodynamics  [Show abstract] [Hide abstract]
ABSTRACT: We study the density driven symmetry breaking in holographic superconductors by considering the positive mass squared case. We show that even for the positive m 2 , a scalar condensation still forms, provided the chemical potential is high enough. As m 2 increases, the phase space folds due to the nonlinearity of the equations of motion, and two nearby points in the phase space can represent symmetry breaking and preserving configurations respectively. The phase space defined by the set of initial conditions of field variables at the horizon undergoes a nonlinear radial evolution to result in the phase space folding, a characteristic phenomenon in a nonlinear system. We then calculate the specific heat, which characterizes superconductors and has been measured in experiments. We observe a discontinuity in the specific heat at the transition point and compare our results with experimentally observed numbers. The electrical conductivity for various m 2 is also calculated.  [Show abstract] [Hide abstract]
ABSTRACT: We study the spectra of light mesons as well as the dissociation of a quarkonium and monopoleanti monopole bound state in a gluon condensate background. In order to describe the confining phase we introduce an IR cutoff in two ways, namely the hard wall and the braneless approaches. We find that the meson spectra strongly depend on the gluon condensate in the braneless approach, while they do not in the hard wall model. The latter result appears to be a more probable feature of QCD. Comment: 16 pages, 5 figures, figures changed, references added, arguments improved, published version  [Show abstract] [Hide abstract]
ABSTRACT: We study the density driven symmetry breaking in holographic superconductors by considering the positive mass squared case. We show that even for the positive $m^2$, a scalar condensation still forms, provided the chemical potential is high enough. As $m^2$ increases, the phase space folds due to the nonlinearity of the equations of motion, and two nearby points in the phase space can represent symmetry breaking and preserving configurations respectively. The phase space defined by the set of initial conditions of field variables at the horizon undergoes a nonlinear radial evolution to result in the phase space folding, a characteristic phenomenon in a nonlinear system. We then calculate the specific heat, which characterizes superconductors and has been measured in experiments.We observe a discontinuity in the specific heat at the transition point and compare our results with experimentally observed numbers. The electrical conductivity for various $m^2$ is also calculated. Comment: 16 pages, v2: title changed, abstract and discussion updated, typos corrected, references added, to appear in PRD  [Show abstract] [Hide abstract]
ABSTRACT: In this paper we propose a way of determining the subleading corrections to the BekensteinHawking black hole entropy by considering a modified generalized uncertainty principle with two parameters. In the context of modified generalized uncertainty principle, coefficients of the correction terms of black hole entropy are written in terms of combination of the parameters. We also calculate corrections to the StefanBoltzman law of Hawking radiation corresponding to modified generalized uncertainty principle. By comparing the entropy with one from black holes in string theory compactified on a CalabiYau manifold, we point out that the topological information of the compactified space can not easily be related to the parameters in modified generalized uncertainty principle.
Publication Stats
63  Citations  
38.68  Total Impact Points  
Top Journals
Institutions

2012

Yonsei University
 Division of Biomedical Engineering
Sŏul, Seoul, South Korea


20102011

Asia Pacific Center for Theoretical Physics
Urusan, Ulsan, South Korea 
Kyung Hee University
 Department of Physics
Sŏul, Seoul, South Korea


20092010

Sogang University
 Department of Physics
Sŏul, Seoul, South Korea
