[en] The drift mobility of carriers in the vitreous Se thin films were measured by the Haynes-Schokley method. It had been shown that the hole mobility was about 0.83 cm³/V-sec and the drift velocity showed no time dependence. It had also been shown that the value of Pool-Frenkel parameter was approximately 2 from the I-V curve. (Author)

[en] Graphene is characterized by chiral electronic excitations. As such it provides a perfect testing ground for the production of Klein pairs (electron/holes). If confirmed, the standard results for barrier phenomena must be reconsidered with, as a byproduct, the accumulation within the barrier of holes. (paper)

[en] Solvent holes were studied in two-laser, two-color experiments in decalin, methylcyclohexane, and cyclohexane solutions containing aromatic solutes. The holes were produced by photoinduced valence band electron transfer from the solvent to the excited doublet states of aromatic radical cations. The d.c. conductivity signals of these rapidly migrating holes exhibit an exponential decay in both decalins and methylcyclohexane. The rate constants for reaction of the solvent holes with various solutes were measured in trans-decalin, mixtures of trans- and cis-decalins, and methylcyclohexane at room temperature

[en] Bekenstein and Hawking saved the second law of thermodynamics near a black hole by assigning to the hole an entropy Ssub(h) proportional to the area of its event horizon. It is tempting to assume that Ssub(h) possesses all the features commonly associated with the physical entropy. Kundt has shown, however, that Ssub(h) violates several reasonable physical expectations. This criticism is reviewed, augmenting it as follows: (a) Ssub(h) is a badly behaved state function requiring knowledge of the hole's future history; and (b) close analogs of event horizons in other space-times do not possess an 'entropy'. These questions are also discussed: (c) Is Ssub(h) suitable for all regions of a black-hole space-time. And (b) should Ssub(h) be attributed to the exterior of a white hole. One can retain Ssub(h) for the interior (respectively, exterior) of a black (respectively, white) hole, but is rejected as contrary to the information-theoretic derivation of horizon entropy given by Berkenstein. The total entropy defined by Kundt (all ordinary entropy on space-section cutting through the hole, no horizon term) and that of Bekenstein-Hawking (ordinary entropy outside horizon plus horizon term) appear to be complementary concepts with separate domains of validity. In the most natural choice, an observer inside a black hole will use Kundt's entropy, and one remaining outside that of Bekenstein-Hawking. (author)

[en] We study the existence of analogue nonstationary spherically symmetric black holes. The prime example is the acoustic model see Unruh (1981 Phys. Rev. Lett. 46 1351). We consider also a more general class of metrics that could be useful in other physical models of analogue black and white holes. We give examples of the appearance of black holes and of disappearance of white holes. We also discuss the relation between the apparent and the event horizons for the case of analogue black holes. In the end we study the inverse problem of determination of black or white holes by boundary measurements for the spherically symmetric nonstationary metrics. (paper)

[en] We consider the question whether a wormhole can be converted into a nonextremal quasiblack hole by a continuous change of parameters. In other words, we ask whether 'black' wormholes can exist as end points of families of static wormhole geometries. The answer is negative since the corresponding limit is singular. Similar conclusions are valid also for other types of black hole mimickers. Our treatment is model independent and applies to any static geometries. We also find an asymptotic expression for the Kretschmann scalar for wormholes on the threshold of horizon formation. We point out complementarity between the ability of wormholes to mimic black holes and their ability to be traversable 'in practice'.

[en] We construct and discuss the form of the (effective) spacetime geometry inside a black hole undergoing a quantum transition to a white hole, taking into account the back-reaction of the component of the Hawking radiation falling into the hole. (paper)

[en] It is shown that, if the quantum resolution limit in the region of a collapsing body near the horizon is of the order of the Schwarzschild radius, a black hole in vacuum evaporates instantaneously. Hence white and black holes ought to be physically indistinguishable and should not physically exist. (author)

[en] In this article a brief logical tour of the concept of black hole is exposed. Following a plot logic by way of personal reading of the history of black holes. (Author)

[en] The AMPS argument for black hole firewalls seems to arise not only from the assumption of local effective field theory outside the stretched horizon but also from an overcounting of internal black hole states that include states that are singular in the past. Here I propose to exclude such singular states by Extreme Cosmic Censorship (the conjectured principle that the universe is entirely nonsingular, except for transient singularities inside black and/or white holes). I argue that the remaining set of nonsingular realistic states do not have firewalls but yet preserve information in Hawking radiation from black holes that form from nonsingular initial states