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

http://cds.cern.ch/record/503806/files/0106045.pdf

New developments in the Casimir effect

This review discusses how low-energy, valence excitations created by swift electrons can render information on the optical response of structured materials with unmatched spatial resolution. Electron microscopes are capable of focusing electron beams on sub-nanometer spots and probing the target response either by analyzing electron energy losses or by detecting emitted radiation. Theoretical frameworks suited to calculate the probability of energy loss and light emission (cathodoluminescence) are revisited and compared with experimental results. More precisely, a quantum-mechanical description of the interaction between the electrons and the sample is discussed, followed by a powerful classical dielectric approach that can be in practice applied to more complex systems. We assess the conditions under which classical and quantum-mechanical formulations are equivalent. The excitation of collective modes such as plasmons is studied in bulk materials, planar surfaces, and nanoparticles. Light emission induced by the electrons is shown to constitute an excellent probe of plasmons, combining sub-nanometer resolution in the position of the electron beam with nanometer resolution in the emitted wavelength. Both electron energy-loss and cathodoluminescence spectroscopies performed in a scanning mode of operation yield snap shots of plasmon modes in nanostructures with fine spatial detail as compared to other existing imaging techniques, thus providing an ideal tool for nanophotonics studies.

/pdf/optical-excitations-in-electron-microscopy-3d2rfnfkst.pdf

Optical excitations in electron microscopy

Part I. Astronomical Background: 1. High energy astrophysics - an introduction 2. The stars and stellar evolution 3. The galaxies 4. Clusters of galaxies Part II. Physical Processes: 5. Ionisation losses 6. Radiation of accelerated charged particles and bremsstrahlung of electrons 7. The dynamics of charged particles in magnetic fields 8. Synchrotron radiation 9. Interactions of high energy photons 10. Nuclear interactions 11. Aspects of plasma physics and magnetohydrodynamics Part III. High Energy Astrophysics in our Galaxy: 12. Interstellar gas and magnetic fields 13. Dead stars 14. Accretion power in astrophysics 15. Cosmic rays 16. The origin of cosmic rays in our galaxy 17. The acceleration of high energy particles Part IV. Extragalactic High Energy Astrophysics: 18. Active galaxies 19. Black holes in the nuclei of galaxies 20. The vicinity of the black hole 21. Extragalactic radio sources 22. Compact extragalactic sources and superluminal motions 23. Cosmological aspects of high energy astrophysics Appendix References Index.

High Energy Astrophysics

It is shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions). A more complete theory is developed. It is shown that excitons are approximate bosons, and, in interaction with the electromagnetic field, the exciton field plays the role of the classical polarization field. The eigenstates of the system of crystal and radiation field are mixtures of photons and excitons. The ordinary one-quantum optical lifetime of an excitation is infinite. Absorption occurs only when "three-body" processes are introduced. The theory includes "local field" effects, leading to the Lorentz local field correction when it is applicable. A Smakula equation for the oscillator strength in terms of the integrated absorption constant is derived.

a Quantum-Mechanical Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals.

Introduction 139 1. Plasma in a Homogeneous Electric Field (Elementary Theory) 141 1.1. Electron Current. Dielectric Permittivity and Conductance of Plasma 141 1.2. Electron Temperature 143 2. Plasma in Homogeneous Electric Fields (Kinetic Theory) 147 2.1. Kinetic Equation 147 2.2. Transformation of the Collision Integral 150 a) Elastic Collisions with Neutral Particles (Molecules) 150 b) Inelastic Collisions with Neutral Particles 152 c) Collisions with Ions 153 d) Collisions between Electrons 154 2.3. Solution of Kinetic Equation. Stronglyionized Plasma 155 a) Distribution Function (Maxwellian Distribution) 156 b) Effective Number of Collisions 158 c) Relative Fraction of Energy Transfer 158 d) Electron Current. Dielectric Permittivity and Conductance of Plasma 159 e) Electron Temperature 162 2.4. Weakly-ionized Plasma 163 a) Case of Elastic Collisions 163 b) Molecular Plasma 164 c) Inert Gases 165 d) Electron Current and Average Electron Energy 166 2.5. Arbitrary Degree of Ionization. Elementary Theory 166 a) Transition for Strongly-ionized to Weakly-ionized Plasma 166 b) Conditions of Validity of Elementary Theory 168 3. Nonlinear Effect in the Propagation of Radio Waves in a Plasma (Ionosphere) 3.1. Propagation of a Radio Wave in a Plasma with Allowance for Nonlinearity (Self Action of the Plasma) 3.2. Role of Self Action of a Plasma in the Propagation of Waves in the Ionosphere a) Short Waves (λ≤ 200 m; ω ≥ 107). b) Average Waves (200 2000 m; ω < 106). d) Resonant Self-remodulation near the Gyro Frequency 3.3. Nonlinear Interaction of Modulated Radio Waves (Cross Modulation), a) Cross Modulation in Isotropic Plasma, b) Calculation of the Effect of a Permanent Magnetic Field. Resonant Effects near the Gyro Frequency 3.4. Results of Experimental Investigations of Cross Modulation in the Ionosphere. a) Absolute Value of Depth of Cross Modulation, b) Dependence of μΩ and ΦΩ on μ0 and Ω, n) Dependence of μΩ on the Power of the Interfering Station, d) Dependence of μΩ on the Frequencies ω1 and ω2. e) Resonance of Cross Modulation at ω1 ~ ωH. 3.5. Nonlinear Interaction of Unmodulated Radio Waves, a) Variation of Conditions of Wave Propagation, b) Sideband Waves (Waves with Combination Frequencies). c) Nonlinear Effects Connected with Variation of the Electron Concentration Concluding Remarks Literature Cited

http://iopscience.iop.org/article/10.1070/PU1960v003n01ABEH003261/pdf

Nonlinear phenomena in a Plasma located in an alternating electromagnetic field

Thirty-three papers are presented on theoretical problems in quantum field theory, elementary particle theory, classical and quantum electrodynamics, and many body quantum theory and solid state theory. Separate abstracts were prepared for twentyfour papers. One paper was previously abstracted for NSA and appeared as 27: 03776. The remaining papers were not within the subject scope of NSA. (LBS)

Problems of theoretical physics

A large number of recent articles are devoted to the theory of Van-der-Waals forces between macroscopic bodies, and to a number of related questions. Attention is being paid both to the solution of various concrete problems and to the development of a general theory. The latter is necessitated by the fact that the Van-der-Waals theory of forces between bodies is known to be quite cumbersome. Through certain efforts, the theory expounded in this review has been simplified in certain respects, and was also generalized. The review describes, first, a "simple" theory of Van-der-Waals forces (Chap. 2), which in our opinion is particularly clear and technically simple without adversely affecting the accuracy of the calculations. Second, we develop and describe a rather common and seemingly sufficiently lucid approach, which permits calculation of the contribution of the long-wave equilibrium electromagnetic field and the thermodynamic characteristics of condensed bodies (Chap. 3). Third, results are presented of a number of concrete calculations for Van-der-Waals forces between bodies (Chap. 4).

http://iopscience.iop.org/article/10.1070/PU1975v018n05ABEH001958/pdf

Electromagnetic fluctuations in matter and molecular (Van-der-Waals) forces between them

The radiation produced by uniformly moving sources (the Vavilov-Cherenkov effect, the transition radiation, and some other phenomena) is discussed. This area of physical research originated in the Lebedev Physical Institute of the Russian Academy of Sciences and now represents an integral part of modern physics.

http://iopscience.iop.org/article/10.1070/PU1996v039n10ABEH000171/pdf

Radiation by uniformly moving sources (Vavilov–Cherenkov effect, transition radiation, and other phenomena)

The rate of development of science nowadays is striking. Great changes in physics, astronomy, biology, and many other fields of science have come about within a period of not more than one to two generations. Readers may see it even in the example of their own families. My father, for instance, was born in 1863 and was a younger contemporary of Maxwell (1831–1879). I myself was already 16 when the neutron and positron were discovered in 1932. Before that only the electron, proton, and photon were known. It is somehow not easy to realize that the electron, X-rays, and radioactivity were discovered only about a hundred years ago, and quantum theory was born in 1900. At the same time, one hundred years is such a short period, not only compared with the approximately 3 billion years since life appeared on the Earth, but also compared with the age of modern man (Homo sapiens), which amounts to nearly 50 thousand years! It is also useful to remember that the first great physicists — Aristotle (384–322 B.C.) and Archimedes (about 287–212 B.C.) are separated from us by more than two thousand years.

/pdf/what-problems-of-physics-and-astrophysics-seem-now-to-be-5a1qon0ij0.pdf

What problems of physics and astrophysics seem now to be especially important and interesting (thirty years later, already on the verge of XXI century)?

Vitalii L Ginzburg

Papers

Nonlinear phenomena in a Plasma located in an alternating electromagnetic field

Problems of theoretical physics

Electromagnetic fluctuations in matter and molecular (Van-der-Waals) forces between them

Radiation by uniformly moving sources (Vavilov–Cherenkov effect, transition radiation, and other phenomena)

What problems of physics and astrophysics seem now to be especially important and interesting (thirty years later, already on the verge of XXI century)?