Effect of helical edge states on the tunneling conductance in ferromagnet/noncentrosymmetric superconductor junction

Helical edge states exist in the mixed spin-singlet and spin-triplet phase of a noncentrosymmetric (NCS) superconductor [Y. Tanaka, T. Yokoyama, A.V. Balatsky, N. Nagaosa, Phys. Rev. B 79, 060505(R) (2009)]. In this article we have considered a planar ferromagnetic metal/NCS superconductor tunnel junction and have studied the effect of these helical edge states which manifests itself through the charge and spin tunneling conductance across the junction. We have shown the behavior of conductance for the entire range of variation of γ = Δ _-/Δ ₊ where Δ _± are the order parameters in the positive and negative helicity bands of the NCS superconductor. There exists a competition between the Rashba parameter α and the exchange energy E _ex which is crucial for determining the variation of the conductance with the applied bias voltage across the junction. We have found a nonzero spin current across the junction which appears due to the exchange energy in the Ferromagnet and modulates with the bias voltage. It also changes its profile when the strength of the exchange energy is varied.     

Unsharpness,Naimark Theorem and Informational Equivalence of Quantum Observables

For each commutative POV measure F there exists (Beneduci, J. Math. Phys. 47:062104-1, 2006; Int. J. Geom. Methods Mod. Phys. 3:1559, 2006) a PV measure E such that F can be interpreted as a random diffusion of E. In its turn, the self-adjoint operator A=∫ λ  dE _λ corresponding to E, can be interpreted (Beneduci, J. Math. Phys. 48:022102-1, 2007; Nuovo Cimento B 123:43–62, 2008) as the projection of a Naimark operator corresponding to the Naimark dilation E ⁺ of F. Moreover E can be algorithmically reconstructed by F. All that suggests that, in some sense, the observables represented by E and F should have the same informational content. We introduce an equivalence relation on the set of observables which we compare with other well known equivalence relations and prove that it is the only one for which E is always equivalent to F.     

Time-resolved hydrino continuum transitions with cutoffs at 22.8 nm and 10.1 nm

Spectra of low energy, high current pinch discharges in pure hydrogen, oxygen, nitrogen, and helium were recorded in the EUV region, and continuum radiation was only observed from hydrogen [www.blacklightpower.com/pdf/GEN3_Harvard.pdf; Int. J. Hydrogen Energy 35, 8446 (2010); Cent. Eur. J. Phys. 8, 318 (2010)]. The continuum radiation bands at 10.1 and 22.8 nm and going to longer wavelengths for theoretically predicted transitions of hydrogen to lower-energy, so called “hydrino” states, was observed first at blacklight power, Inc. (BLP) and reproduced at the Harvard center for astrophysics (CfA). Considering the low energy of 5.2 J per pulse, the observed radiation in the energy range of about 120 eV to 40 eV and reference experiments, no conventional explanation was found to be plausible, including electrode metal emission, Bremsstrahlung radiation, ion recombination, molecular or molecular ion band radiation, and instrument artifacts involving radicals and energetic ions reacting at the CCD and H₂ re-radiation at the detector chamber. To further study these continuum bands assigned to hydrinos, time resolved spectra were performed that showed a unique delay of the continuum radiation of about 0.1 μs and a duration of < 2   μs following the high-voltage pulse consistent with the mechanism of recombination to form the optimal high-density atomic hydrogen in the pinch that permits the H–H interactions to cause the hydrino transitions and corresponding emission.     

Statistical mechanics of Fofonoff flows in an oceanic basin

We study the minimization of potential enstrophy at fixed circulation and energy in an oceanic basin with arbitrary topography. For illustration, we consider a rectangular basin and a linear topography h = by which represents either a real bottom topography or the β-effect appropriate to oceanic situations. Our minimum enstrophy principle is motivated by different arguments of statistical mechanics reviewed in the article. It leads to steady states of the quasigeostrophic (QG) equations characterized by a linear relationship between potential vorticity q and stream function ψ. For low values of the energy, we recover Fofonoff flows [J. Mar. Res. 13, 254 (1954)] that display a strong westward jet. For large values of the energy, we obtain geometry induced phase transitions between monopoles and dipoles similar to those found by Chavanis and Sommeria [J. Fluid Mech. 314, 267 (1996)] in the absence of topography. In the presence of topography, we recover and confirm the results obtained by Venaille and Bouchet [Phys. Rev. Lett. 102, 104501 (2009)] using a different formalism. In addition, we introduce relaxation equations towards minimum potential enstrophy states and perform numerical simulations to illustrate the phase transitions in a rectangular oceanic basin with linear topography (or β-effect).     

Magnetostriction of terbium molybdate in high magnetic field

Magnetostriction and magnetization M of Tb₂(MoO₄)₃ samples are measured at temperatures T = 4.2 and 20 K in fields H up to 14 T directed along the polar axis [001]. Results of the magnetostriction measurements obey the first law of thermodynamics: -MH = TΔS - W_E, where ΔS is the change of the entropy and W_E is the work of internal electric field done when ions move due to the magnetostriction.     

Relaxation equations for two-dimensional turbulent flows with a prior vorticity distribution

Using a Maximum Entropy Production Principle (MEPP), we derive a new type of relaxation equations for two-dimensional turbulent flows in the case where a prior vorticity distribution is prescribed instead of the Casimir constraints [R. Ellis, K. Haven, B. Turkington, Nonlinearity 15, 239 (2002)]. The particular case of a Gaussian prior is specifically treated in connection to minimum enstrophy states and Fofonoff flows. These relaxation equations are compared with other relaxation equations proposed by Robert and Sommeria [Phys. Rev. Lett. 69, 2776 (1992)] and Chavanis [Physica D 237, 1998 (2008)]. They can serve as numerical algorithms to compute maximum entropy states and minimum enstrophy states with appropriate constraints. We perform numerical simulations of these relaxation equations in order to illustrate geometry induced phase transitions in geophysical flows.     

Effects of high-j intruder states in the fine structure of superdeformed bands

All known cases of ΔI=4 bifurcation in superdeformed bands are analyzed on the basis of the theory proposed by the author in a previous paper [I. M. Pavlichenkov, Phys. Rev. C 55, 1275 (1997)]. It is shown that the high-j intruder single-particle states play a critical role in the phenomenon. The bands in which fine structure can be observed are predicted. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 759–764 (25 December 1997)     

Acceleration of pπ-atoms in a Coulomb de-excitation cascade

An improved adiabatic approach (IAA) previously proposed in atomic physics is extended to the case of collisions of mesic atoms in excited states n⩾2. The computed rates λ _nn′ ^C (E) of the Coulomb de-excitation processes (pπ)_n+p→(pπ) _n′+p are substantially different from the IAA results. It is shown that the Coulomb de-excitation rates λ _nn′ ^C are high enough to explain the appearance of pπ mesic atoms with kinetic energy ∼70 eV, which were observed in [J. E. Crawford, M. Daum, R. Frosch, et al., Phys. Lett. B 213, 391 (1988) and Phys. Rev. D 43, 46 (1991)]. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 129–133 (10 August 1996)     

Dynamics of geometric discord and measurement-induced nonlocality at finite temperature

By using geometric measure of discord (GMOD) [B. Dakić, V. Vedral, Č. Brukner, Phys. Rev. Lett. 105, 109502 (2010)] and measurement-induced nonlocality (MIN) [S. Luo, S. Fu, Phys. Rev. Lett. 106, 120401 (2011)], we investigate quantum correlation of a pair of two-level systems, each of which is interacting with a reservoir at finite temperature T. We show that, for a broad class of states of the system, GMOD and MIN can endure sudden death, and there is no asymptotic decay for MIN while asymptotic decay exists for GMOD. We also give the dynamics of GMOD and MIN with respect to the temperature and illustrate their different characteristics.     

Unravelling the size distribution of social groups with information theory in complex networks

The minimization of Fisher’s information (MFI) approach of Frieden et al. [Phys. Rev. E 60, 48 (1999)] is applied to the study of size distributions in social groups on the basis of a recently established analogy between scale invariant systems and classical gases [Phys. A 389, 490 (2010)]. Going beyond the ideal gas scenario is seen to be tantamount to simulating the interactions taking place, for a competitive cluster growth process, in a scale-free ideal network – a non-correlated network with a connection-degree’s distribution that mimics the scale-free ideal gas density distribution. We use a scaling rule that allows one to classify the final cluster-size distributions using only one parameter that we call the competitiveness, which can be seen as a measure of the strength of the interactions. We find that both empirical city-size distributions and electoral results can be thus reproduced and classified according to this competitiveness-parameter, that also allow us to infer the maximum number of stable social relationships that one person can maintain, known as the Dunbar number, together with its standard deviation. We discuss the importance of this number in connection with the empirical phenomenon known as “six-degrees of separation”. Finally, we show that scaled city-size distributions of large countries follow, in general, the same universal distribution.     

A new lattice measurement for potentials between static SU(3) sources

In this article, a new calculation of the static potentials between sources of different representations in SU(3) gauge group is presented. The results of the author’s previous study [Phys. Rev. D 62, 034509 (2000)] at the smallest lattice spacing a_s≃0.11 fm are shown to have been affected by finite volume effects. Within statistical errors, the new results obtained here are still in agreement with both Casimir scaling and flux tube counting. There is also no contradiction to the results obtained by Bali [Phys. Rev. D 62, 114503 (2000)] which however exclude flux counting. PACS 11.15.Ha; 12.38.Aw; 12.39.Pn; 12.38.Gc     

Quantum Gravitational Corrections to the Real Klein-Gordon Field in the Presence of a Minimal Length

The (D+1)-dimensional (β,β′)-two-parameter Lorentz-covariant deformed algebra introduced by Quesne and Tkachuk (J. Phys., A Math. Gen. 39, 10909, 2006), leads to a nonzero minimal uncertainty in position (minimal length). The Klein-Gordon equation in a (3+1)-dimensional space-time described by Quesne-Tkachuk Lorentz-covariant deformed algebra is studied in the case where β′=2β up to first order over deformation parameter β. It is shown that the modified Klein-Gordon equation which contains fourth-order derivative of the wave function describes two massive particles with different masses. We have shown that physically acceptable mass states can only exist for b < \frac18m²c²\beta<\frac{1}{8m^{2}c^{2}} which leads to an isotropic minimal length in the interval 10⁻¹⁷ m<(ΔX ⁱ )₀<10⁻¹⁵ m. Finally, we have shown that the above estimation of minimal length is in good agreement with the results obtained in previous investigations.     

Fermion zero modes on vortices in chiral superconductors

The energy levels of fermions bound to the vortex core are considered for the general case of chiral superconductors. There are two classes of chiral superconductivity: in the class I superconducting state the axisymmetric singly quantized vortex has the same energy spectrum of bound states as in an s-wave superconductor: E=(n+1/2)ω₀, with integral n. In class II the corresponding spectrum is E=nω₀ and thus contains a state with exactly zero energy. The effect of a single impurity on the spectrum of bound states is also considered. For class I the spectrum acquires the doubled period ΔE=2ω₀ and consists of two equidistant sets of levels, in accordance with A. I. Larkin and Yu. N. Ovchinnikov, Phys. Rev. B 57, 5457 (1998). For the class II states the spectrum is not influenced by a single impurity if the same approximation is applied. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 9, 601–606 (10 November 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Asymptotic normalization coefficients (nuclear vertex constants) for p + 7Be → 8B and the direct 7Be(p, γ)8B astrophysical S factors at solar energies

A new analysis of the precise experimental astrophysical S factors for the direct-capture reaction ⁷Be(p, γ)⁸B [A.J. Junghans et al., Phys. Rev. C 68, 065803 (2003) and L.T. Baby et al., Phys. Rev. C 67, 065805 (2003)] is carried out on the basis of a modified two-body potential approach in which the direct astrophysical S factor, S ₁₇(E), is expressed in terms of the asymptotic normalization constants for p + ⁷Be → ⁸B and two additional conditions are involved to verify the peripheral character of the reaction under consideration. The Woods-Saxon potential form is used for the bound-(p + ⁷Be)-state wave function and for p ⁷Be-scattering wave function. New estimates are obtained for the “indirectly measured” values of the asymptotic normalization constants (the nuclear vertex constants) for the p + ⁷Be → ⁸B and S ₁₇(E) at E ≤ 115 keV, including E = 0. These values of S ₁₇(E) and asymptotic normalization constants have been used for obtaining the indirectly measured values of the s-wave average scattering length and the p-wave effective-range parameters for p ⁷Be scattering. The text was submitted by the authors in English.     

Radiative energy loss of high-energy quarks in finite-size nuclear matter and quark-gluon plasma

The induced gluon radiation of a high-energy quark in a finite-size QCD medium is studied. For a sufficiently energetic quark produced inside a medium we find the radiative energy loss ΔE _q∝L ², where L is the distance traveled by quark in the medium. It has a weak dependence on the initial quark energy E _q. The L ² dependence turns to L ¹ as the quark energy decreases. Numerical calculations are performed for a cold nuclear matter and a hot quark-gluon plasma. For a quark incident on a nucleus we predict ΔE _q ≈0.1E _q (L/10fm) ^β , with β close to unity. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 585–589 (25 April 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Shaping of the electron distribution function in a striated solution

Numerous papers have been devoted to the investigation of striations in inert gases at low pressures (p⩽2 Torr) and small currents (i<100 mA) [A. V. Nedospasov, Sov. Phys. Usp. 11, 174 (1968); L. Pekarek, Sov. Phys. Usp. 11, 188 (1968); N. L. Oleson and A. W. Cooper, Adv. Electron. Electron Phys. 24, 155 (1968); P. S. Landa, N. A. Miskinova, and Yu. V. Ponomarev, Sov. Phys. Usp. 23, 813 (1980)]. Since the nature of striations is determined under these conditions by the nonlocal kinetics of the electrons in spatially periodic fields [L. D. Tsendin, Sov. J. Plasma Phys. 8, 228 (1982)], an investigation of the electron distribution function in space and time would be very interesting. The purpose of the present work is to experimentally investigate the potential profiles and distribution functions in S and P striations and to analyze the mechanism which shapes the distribution functions for striations of these types. Zh. Tekh. Fiz. 67, 14–21 (September 1997)     

Symmetry and integrability for stochastic differential equations

We discuss the interrelations between symmetry of an Ito stochastic differential equations (or systems thereof) and its integrability, extending in party results by R. Kozlov [J. Phys. A 43 (2010) & 44 (2011)]. Together with integrability, we also consider the relations between symmetries and reducibility of a system of SDEs to a lower dimensional one. We consider both “deterministic” symmetries and “random” ones, in the sense introduced recently by Gaeta and Spadaro [J. Math. Phys. 58 (2017)].     

Einstein-Podolsky-Rosen paradox,Bell's inequality,and the projection postulate

Our aim is to understand the role of implicit assumptions which has been used by Einstein, Podolsky, and Rosen (EPR) in their famous article [Phys. Rev., 47, 777 (1935)] devoted to the so-called EPR paradox. We found that the projection postulate plays a crucial role in the EPR argument. It seems that EPR made a mistake in this paper — the projection postulate was applied not in its original form (as it has been formulated in von Neumann's book [Mathematical Foundations of Quantum mechanics, Princeton University Press (1955)] but in the form which was later formalized as Lüders' postulate [Ann. Phys., Lpz. 8, 322 (1951)]. Von Neumann's postulate was crucially modified by extending it to observables with degenerate spectra. This modification is the real source of “quantum nonlocality.” The use of the original von Neumann postulate eliminates this problem — instead of (an action at a distance)-nonlocality, we obtain a classical measurement nonlocality, which is related to the synchronization of two measurements (produced on the two parts of a composite system). If one uses correctly von Neumann's projection postulate, no “elements of reality” can be assigned to entangled systems. Talk presented at the oral issue of J. Russ. Laser Res. dedicated to the memory of Professor Vladimir A. Isakov, Professor Alexander S. Shumovsky, and Professor Andrei V. Vinogradov held in Moscow February 21–22, 2008.     

On the optimality of individual entangling-probe attacks against BB84 quantum key distribution

Some MIT researchers [Phys. Rev. A 75, 042327 (2007)] have recently claimed that their implementation of the Slutsky-Brandt attack [Phys. Rev. A 57, 2383 (1998); Phys. Rev. A 71, 042312 (2005)] to the BB84 quantum-key-distribution (QKD) protocol puts the security of this protocol “to the test” by simulating “the most powerful individual-photon attack” [Phys. Rev. A 73, 012315 (2006)]. A related unfortunate news feature by a scientific journal [G. Brumfiel, Quantum cryptography is hacked, News @ Nature (april 2007); Nature 447, 372 (2007)] has spurred some concern in the QKD community and among the general public by misinterpreting the implications of this work. The present article proves the existence of a stronger individual attack on QKD protocols with encrypted error correction, for which tight bounds are shown, and clarifies why the claims of the news feature incorrectly suggest a contradiction with the established “old-style” theory of BB84 individual attacks. The full implementation of a quantum cryptographic protocol includes a reconciliation and a privacy-amplification stage, whose choice alters in general both the maximum extractable secret and the optimal eavesdropping attack. The authors of [Phys. Rev. A 75, 042327 (2007)] are concerned only with the error-free part of the so-called sifted string, and do not consider faulty bits, which, in the version of their protocol, are discarded. When using the provably superior reconciliation approach of encrypted error correction (instead of error discard), the Slutsky-Brandt attack is no more optimal and does not “threaten” the security bound derived by Lütkenhaus [Phys. Rev. A 59, 3301 (1999)]. It is shown that the method of Slutsky and collaborators [Phys. Rev. A 57, 2383 (1998)] can be adapted to reconciliation with error correction, and that the optimal entangling probe can be explicitly found. Moreover, this attack fills Lütkenhaus bound, proving that it is tight (a fact which was not previously known).