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Jae-Weon Lee

Publications and source records attributed to Jae-Weon Lee.

50 records · Page 3Linked to original sources
arXiv2008

Cosmological Imprint of the Second Law of Thermodynamics

We study the evolution of the universe in the presence of inflaton, matter, radiation, and holographic dark energy. The time evolution of the scale factor is obtained by solving the Friedmann equation of the universe with a good approximation. We present two independent ways which determine the value of the dark energy constant $d\sim 1$ from the observational data. The two ways are measuring the deceleration parameter and measuring a universal constant depending only on $d$. The universal constant is given by a dimensionless combination of three scale factors at the equipartition times of radiation-matter, radiation-dark energy, and matter-dark energy. We also discuss that the second law of thermodynamics determines the point of time when the dark energy dominated era begins in the universe.

gr-qc↗
arXiv2008

BEC dark matter can explain collisions of galaxy clusters

We suggest that the dark matter model based on Bose Einstein condensate or scalar field can resolve the apparently contradictory behaviors of dark matter in the Abell 520 and the Bullet cluster. During a collision of two galaxies in the cluster, if initial kinetic energy of the galaxies is large enough, two dark matter halos pass each other in a soliton-like way as observed in the Bullet cluster. If not, the halos merge due to the tiny repulsive interaction among dark matter particles as observed in the Abell 520. This idea can also explain the origin of the dark galaxy and the galaxy without dark matter.

hep-ph↗
arXiv2008

Quantum Informational Dark Energy: Dark energy from forgetting

We suggest that dark energy has a quantum informational origin. Landauer's principle associated with the erasure of quantum information at a cosmic horizon implies the non-zero vacuum energy having effective negative pressure. Assuming the holographic principle, the minimum free energy condition, and the Gibbons-Hawking temperature for the cosmic event horizon we obtain the holographic dark energy with the parameter $d\simeq 1$, which is consistent with the current observational data. It is also shown that both the entanglement energy and the horizon energy can be related to Landauer's principle.

hep-th↗
arXiv2008

Dark energy, inflation and the cosmic coincidence problem

We show that holographic dark energy could explain why the current dark energy density is so small, if there was an inflation with a sufficient expansion in the early universe. It is also suggested that an inflation with the number of e-folds $N\simeq 65$ may solve the cosmic coincidence problem in this context. Assuming the inflation and the power-law acceleration phase today we obtain approximate formulas for the event horizon size of the universe and dark energy density as functions of time. A simple numerical study exploiting the formula well reproduces the observed evolution of dark energy. This nontrivial match between the theory and the observational data supports both inflation and holographic dark energy models.

hep-th↗
arXiv2007

Dark energy from vacuum entanglement

We suggest that vacuum entanglement energy associated with the entanglement entropy of the universe is the origin of dark energy. The observed properties of dark energy can be explained by using the nature of entanglement energy without modification of gravity or exotic matter. From the number of degrees of freedom in the standard model, we obtain the equation of state parameter $ω^0_Λ\simeq -0.93$ and $d\simeq 0.95$ for the holographic dark energy, which are consistent with current observational data at the 95% confidence level.

hep-th↗
arXiv2007

Bremsstrahlung Radiation At a Vacuum Bubble Wall

When charged particles collide with a vacuum bubble, they can radiate strong electromagnetic waves due to rapid deceleration. Owing to the energy loss of the particles by this bremsstrahlung radiation, there is a non-negligible damping pressure acting on the bubble wall even when thermal equilibrium is maintained. In the non-relativistic region, this pressure is proportional to the velocity of the wall and could have influenced the bubble dynamics in the early universe.

hep-th↗
arXiv2007

Entanglement of thermal scalar fields in a compact space space

Using the thermal Green's function approach we propose a general method to investigate entanglement of the vacuum state or thermal ground states in an arbitrary dimensional space-time. As an application we show quantum separability of the massive thermal scalar field vacuum in the 1+1 dimensional cylindrical space-time. Separability is demonstrated using the positive partial transpose criterion for effective two-mode Gaussian states of collective operators. In this case, for all mass and temperature values entanglement is absent between the collective operators.

quant-ph↗
arXiv2006

Quantum Separability of Thermal Spin One Boson Systems

Using the temperature Green's function approach we investigate entanglement between two non-interacting spin 1 bosons in thermal equilibrium. We show that, contrary to the fermion case, the entanglement is absent in the spin density matrix. Separability is demonstrated using the Peres-Horodecki criterion for massless particles such as photons in black body radiation. For massive particles, we show that the density matrix can be decomposed with separable states.

quant-ph↗
arXiv2006

Quantum Separability of the vacuum for Scalar Fields with a Boundary

Using the Green's function approach we investigate separability of the vacuum state of a massless scalar field with a single Dirichlet boundary. Separability is demonstrated using the positive partial transpose criterion for effective two-mode Gaussian states of collective operators. In contrast to the vacuum energy, entanglement of the vacuum is not modified by the presence of the boundary.

quant-ph↗
arXiv2005

Quantum key distribution using superposition of the vacuum and single photon states

B92-type and BB84-type quantum cryptography schemes using superposed states of the vacuum and single particle states which are robust against PNS attacks are studied. The number of securely transferred classical bits per particle (not per qubit) sent in these schemes is calculated and found to have upper bounds. Possible experimental realizations using the cavity QED or linear optics are suggested.

quant-ph↗
arXiv2003

Quantum Cryptography Using Single Particle Entanglement

A quantum cryptography scheme based on entanglement between a single particle state and a vacuum state is proposed. The scheme utilizes linear optics devices to detect the superposition of the vacuum and single particle states. Existence of an eavesdropper can be detected by using a variant of Bell's inequality.

quant-ph↗
arXiv2001

Calculation of Magnetic Penetration Depth Length $λ(T)$ in High Tc Superconductors

The notion of a finite pairing interaction energy range via Nam, results in the incomplete condensation in which not all states participate in pairings. Thestates not participating in pairings are shown to yield the lowenergy states responsible for the linear T dependence ofsuperelectron density at low T in a s-wave superconductor. Wepresent extensive quantitative calculations of $λ$(T) forall T ranges, in good agreements with experiments. It is notnecessary to have nodes in the order parameter, to account for thelinear T dependence of $λ$(T) at low T in high Tc superconductors.

cond-mat.supr-con↗