Quantum mechanics: Myths and facts

A common understanding of quantum mechanics (QM) among students and practical users is often plagued by a number of "myths", that is, widely accepted claims on which there is not really a general consensus among experts in foundations of QM. These myths include wave-particle duality, time-energy uncertainty relation, fundamental randomness, the absence of measurement-independent reality, locality of QM, nonlocality of QM, the existence of well-defined relativistic QM, the claims that quantum field theory (QFT) solves the problems of relativistic QM or that QFT is a theory of particles, as well as myths on black-hole entropy. The fact is that the existence of various theoretical and interpretational ambiguities underlying these myths does not yet allow us to accept them as proven facts. I review the main arguments and counterarguments lying behind these myths and conclude that QM is still a not-yet-completely-understood theory open to further fundamental research.Comment: 51 pages, pedagogic review, revised, new references, to appear in Found. Phy

Boson-fermion unification, superstrings, and Bohmian mechanics

Bosonic and fermionic particle currents can be introduced in a more unified way, with the cost of introducing a preferred spacetime foliation. Such a unified treatment of bosons and fermions naturally emerges from an analogous superstring current, showing that the preferred spacetime foliation appears only at the level of effective field theory, not at the fundamental superstring level. The existence of the preferred spacetime foliation allows an objective definition of particles associated with quantum field theory in curved spacetime. Such an objective definition of particles makes the Bohmian interpretation of particle quantum mechanics more appealing. The superstring current allows a consistent Bohmian interpretation of superstrings themselves, including a Bohmian description of string creation and destruction in terms of string splitting. The Bohmian equations of motion and the corresponding probabilistic predictions are fully relativistic covariant and do not depend on the preferred foliation.Comment: 30 pages, 1 figure, revised, to appear in Found. Phy

Black-hole information puzzle: A generic string-inspired approach

Given the insight steming from string theory, the origin of the black-hole (BH) information puzzle is traced back to the assumption that it is physically meaningful to trace out the density matrix over negative-frequency Hawking particles. Instead, treating them as virtual particles necessarily absorbed by the BH in a manner consistent with the laws of BH thermodynamics, and tracing out the density matrix only over physical BH states, the complete evaporation becomes compatible with unitarity.Comment: 8 pages, revised, title changed, to appear in Eur. Phys. J.

Generalizations of normal ordering and applications to quantization in classical backgrounds

A nonlocal method of extracting the positive (or the negative) frequency part of a field, based on knowledge of a 2-point function, leads to certain natural generalizations of the normal ordering of quantum fields in classical gravitational and electromagnetic backgrounds and illuminates the origin of the recently discovered nonlocalities related to a local description of particles. A local description of particle creation by gravitational backgrounds is given, with emphasis on the case of black-hole evaporation. The formalism reveals a previously hidden relation between various definitions of the particle current and those of the energy-momentum tensor. The implications to particle creation by classical backgrounds, as well as to the relation between vacuum energy, dark matter, and cosmological constant, are discussed.Comment: 17 pages, revised, title shortened, to appear in Gen. Rel. Gra

Conformations in unsymmetrically N-n-propyl-N-substituted 2-phenylacetamides

As a part of a study on the structural characteristics of some new various N-alkyl-N-substituted 2-phenylacetamides the infrared and 1H N.M.R. spectra were obtained and interpreted. The synthesis of a various N-n-propyl-N-alkyl 2-phenylacetamides of the general formula PhCH2CON(nPr)R, wherein R is ethyl, isopropyl, n-butyl, t-butyl and cyclohexyl, were performed. The corresponding mixed secondary amines of the type HNnPrR were obtained by catalytic hydrogenation of the synthetized propylidenealkylamines. The 1H N.M.R. spectra of these unsymmetrically N,N-disubstituted amides have been studied and the peaks have been assigned in each cases to two possible conformational isomers, arising from the lack of free rotation about the C(O)N bond. These results are in accordance with our previous investigation of the structure of N-substituted 2-phenylacetamides

The effect of deposition process exchange current density on the thin metal film formation on inert substrate

The initial stage of thin surface metal film formation on inert substrate is considered. The simultaneous action of both active centers and nucleation exclusion zones was taken into consideration when discussing the saturation nucleus density. The saturation nucleus density increases with increasing number of active centers and decreasing the radii of nucleation exclusion zones (enhancing the thin metal film formation). At one at the same deposition current density deposition overpotential increases with decreasing deposition process exchange current density, leading to the increase in the number of active centers and to decrease of crystallization overpotential and radii of nucleation exclusion zones. Because of this compact surface metal film will be formed at a lower quantity of electrodeposited metal with a decrease in exchange current density

The particle size distribution (PSD) as criteria for comparison of silver powders obtained by different methods of synthesis and by conditions of electrolysis

Silver powders produced by both electrochemical (galvanostatic (DC) and potentiostatic (POT) regimes of electrolysis) and chemical processes were examined by scanning electron microscope, and particle size distribution (PSD) of the obtained particles was done. In the DC regime, the current densities of –14.4 mA cm-2 for the nitrate (NIT; powder denoted with DC(NIT)) and –13.05 mA cm-2 for the ammonium (AM; DC(AM)) electrolytes were applied. In the POT regime, the used overpotentials were –90 mV (NIT(90)) and –150 mV (NIT(150)) for the nitrate, and –625 mV (AM(625)) and –925 mV (AM(925)) for the ammonium electrolytes. Reduction with hydrazine was used for chemical synthesis (powder denoted with HYD). On the basis of SEM and PSD analysis, Ag powders were grouped into three groups. In the first group DC(AM), AM(925) and HYD powders with the (8.4–8.9 %) volume ratios were placed. In the second group were AM(625) and DC(NIT) powders with the (6.5–6.6 %) volume ratios. NIT(90) and NIT(150) powders with the volume ratios of (5.2–5.7 %) made the third group. The obtained volume ratios were correlated with the morphology of synthesized particles in order to perceive advantages and lacks of powder production via electrochemical and chemical routes