[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

QUANTUM gravitational effects are usually ignored in calculations of the formation and evolution of black holes. The justification for this is that the radius of curvature of space-time outside the event horizon is very large compared to the Planck length (Għ/c3)1/2 ≈ 10−33 cm, the length scale on which quantum fluctuations of the metric are expected to be of order unity. This means that the energy density of particles created by the gravitational field is small compared to the space-time curvature. Even though quantum effects may be small locally, they may still, however, add up to produce a significant effect over the lifetime of the Universe ≈ 1017 s which is very long compared to the Planck time ≈ 10−43 s. The purpose of this letter is to show that this indeed may be the case: it seems that any black hole will create and emit particles such as neutrinos or photons at just the rate that one would expect if the black hole was a body with a temperature of (κ/2π) (ħ/2k) ≈ 10−6 (M/M)K where κ is the surface gravity of the black hole1. As a black hole emits this thermal radiation one would expect it to lose mass. This in turn would increase the surface gravity and so increase the rate of emission. The black hole would therefore have a finite life of the order of 1071 (M/M)−3 s. For a black hole of solar mass this is much longer than the age of the Universe. There might, however, be much smaller black holes which were formed by fluctuations in the early Universe2. Any such black hole of mass less than 1015 g would have evaporated by now. Near the end of its life the rate of emission would be very high and about 1030 erg would be released in the last 0.1 s. This is a fairly small explosion by astronomical standards but it is equivalent to about 1 million 1 Mton hydrogen bombs. It is often said that nothing can escape from a black hole. But in 1974, Stephen Hawking realized that, owing to quantum effects, black holes should emit particles with a thermal distribution of energies — as if the black hole had a temperature inversely proportional to its mass. In addition to putting black-hole thermodynamics on a firmer footing, this discovery led Hawking to postulate 'black hole explosions', as primordial black holes end their lives in an accelerating release of energy.

Black Hole Explosions

Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

Monthly Notices of the Royal Astronomical Society

KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded.

First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance

Annals of physics

We perform the first global QCD analysis of parton distribution functions (PDFs) in the pion, combining πA Drell-Yan data with leading neutron electroproduction from HERA within a Monte Carlo approach based on nested sampling. Inclusion of the HERA data allows the pion PDFs to be determined down to much lower values of x, with relatively weak model dependence from uncertainties in the chiral splitting function. The combined analysis reveals that gluons carry a significantly higher pion momentum fraction, ∼30%, than that inferred from Drell-Yan data alone, with sea quarks carrying a somewhat smaller fraction, ∼15%, at the input scale. Within the same effective theory framework, the chiral splitting function and pion PDFs can be used to describe the d[over ¯]-u[over ¯] asymmetry in the proton.

First Monte Carlo Global QCD Analysis of Pion Parton Distributions

A comprehensive, relativistic many-body approach to hadron structure is advanced based on the Coulomb gauge QCD Hamiltonian. Dynamical chiral symmetry breaking naturally emerges, and both quarks and gluons acquire constituent masses when standard many-body techniques are employed. Gluonia are studied both in the valence and in the collective, random phase approximations. Calculated quenched glueball masses are found to be in remarkable agreement with lattice gauge theory when using representative values for the strong coupling constant and string tension. {copyright} {ital 1996 The American Physical Society.}

Glueball spectroscopy in a relativistic many-body approach to hadronic structure.

The asymptotic large-momentum-transfer behavior of the deuteron form factor and the form of the deuteron distribution amplitude at short distances are derived from perturbative quantum chromodynamics. The fact that the six-quark state is 80% hidden color at small transverse separation implies that the deuteron form factors cannot be described at large ${Q}^{2}$ by meson-nucleon degrees of freedom, and that the nucleon-nucleon potential is repulsive at short distances.

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Quantum Chromodynamic Predictions for the Deuteron Form Factor

Both the mass spectra and the wave functions of the light pseudoscalar $(\ensuremath{\pi},K,\ensuremath{\eta},{\ensuremath{\eta}}^{\ensuremath{'}})$ and vector$(\ensuremath{\rho}{,K}^{*},\ensuremath{\omega},\ensuremath{\varphi})$ mesons are analyzed within the framework of the light-cone constituent quark model. A Gaussian radial wave function is used as a trial function of the variational principle for a QCD-motivated Hamiltonian which includes not only the Coulomb plus confining potential but also the hyperfine interaction to obtain the correct $\ensuremath{\rho}$-$\ensuremath{\pi}$ splitting. For the confining potential, we use the (1) harmonic oscillator potential and (2) linear potential and compare the numerical results for these two cases. The mixing angles of $\ensuremath{\omega}$-$\ensuremath{\varphi}$ and $\ensuremath{\eta}$-${\ensuremath{\eta}}^{\ensuremath{'}}$ are predicted and various physical observables such as decay constants, charge radii, and radiative decay rates, etc., are calculated. Our numerical results in the two cases (1) and (2) are overall not much different from each other and are in good agreement with the available experimental data.

Mixing angles and electromagnetic properties of ground state pseudoscalar and vector meson nonets in the light-cone quark model

Using our previously developed crossing and duality consistent model for kaon photoproduction and radiative capture, we investigate the kaon electroproduction processes p(e,e'${\mathit{K}}^{+}$)Y for Y=\ensuremath{\Lambda}, ${\mathrm{\ensuremath{\Sigma}}}^{0}$, and \ensuremath{\Lambda}(1405). Because there is no electroproduction data near threshold, consistency requires extending the energy range of our photoproduction model parametrization from an upper bound of ${\mathit{E}}_{\ensuremath{\gamma}}^{\mathrm{lab}}$=1.4 to 2.2 GeV. We find that baryon resonances with spin greater than 1/2 are necessary to describe the higher energy photoproduction data (1.4\ensuremath{\le}${\mathit{E}}_{\ensuremath{\gamma}}^{\mathrm{lab}}$\ensuremath{\le}2.2 GeV). We also extend our use of duality by representing these higher-spin s- and u-channel baryon resonances with the low-lying t-channel vector, ${\mathit{K}}^{\mathrm{*}}$(890), and pseudovector, ${\mathit{K}}_{1}$(1270), mesons. Using this extended crossing and duality consistent model, we obtain reasonable agreement with the data for both photoproduction and electroproduction processes.

Chueng-Ryong Ji

Papers

First Monte Carlo Global QCD Analysis of Pion Parton Distributions

Glueball spectroscopy in a relativistic many-body approach to hadronic structure.

Quantum Chromodynamic Predictions for the Deuteron Form Factor

Mixing angles and electromagnetic properties of ground state pseudoscalar and vector meson nonets in the light-cone quark model

Hyperon electroproduction in a crossing and duality constrained model.