6,953 research outputs found
Quaternionic potentials in non-relativistic quantum mechanics
We discuss the Schrodinger equation in presence of quaternionic potentials.
The study is performed analytically as long as it proves possible, when not, we
resort to numerical calculations. The results obtained could be useful to
investigate an underlying quaternionic quantum dynamics in particle physics.
Experimental tests and proposals to observe quaternionic quantum effects by
neutron interferometry are briefly reviewed.Comment: 21 pages, 16 figures (ps), AMS-Te
Spectral properties of a two-orbital Anderson impurity model across a non-Fermi liquid fixed point
We study by NRG the spectral properties of a two-orbital Anderson impurity
model in the presence of an exchange splitting which follows either regular or
inverted Hund's rules. The phase diagram contains a non-Fermi liquid fixed
point separating a screened phase, where conventional Kondo effect occurs, from
an unscreened one, where the exchange-splitting takes care of quenching the
impurity degrees of freedom. On the Kondo screened side close to this fixed
point the impurity density of states shows a narrow Kondo-peak on top of a
broader resonance. This narrow peak transforms in the unscreened phase into a
narrow pseudo-gap inside the broad resonance. Right at the fixed point only the
latter survives. The fixed point is therefore identified by a jump of the
density of states at the chemical potential. We also show that particle-hole
perturbations which simply shift the orbital energies do not wash out the fixed
point, unlike those perturbations which hybridize the two orbitals.
Consequently the density-of-state jump at the chemical potential remains finite
even away from particle-hole symmetry, and the pseudo-gap stays pinned at the
chemical potential, although it is partially filled in. We also discuss the
relevance of these results for lattice models which map onto this Anderson
impurity model in the limit of large lattice-coordination. Upon approaching the
Mott metal-insulator transition, these lattice models necessarily enter a
region with a local criticality which reflects the impurity non-Fermi liquid
fixed point. However, unlike the impurity, the lattice can get rid of the
single-impurity fixed-point instability by spontaneously developing
bulk-coherent symmetry-broken phases, which we identify for different lattice
models.Comment: 43 pages, 11 figures. Minor corrections in the Appendi
Quaternionic Electroweak Theory and CKM Matrix
We find in our quaternionic version of the electroweak theory an apparently
hopeless problem: In going from complex to quaternions, the calculation of the
real-valued parameters of the CKM matrix drastically changes. We aim to explain
this quaternionic puzzle.Comment: 8, Revtex, Int. J. Theor. Phys. (to be published
Mutual Inductance Route to Paramagnetic Meissner Effect in 2D Josephson Junction Arrays
We simulate two-dimensional Josephson junction arrays, including full mutual-
inductance effects, as they are cooled below the transition temperature in a
magnetic field. We show numerical simulations of the array magnetization as a
function of position, as detected by a scanning SQUID which is placed at a
fixed height above the array. The calculated magnetization images show striking
agreement with the experimental images obtained by A. Nielsen et al. The
average array magnetization is found to be paramagnetic for many values of the
applied field, confirming that paramagnetism can arise from magnetic screening
in multiply-connected superconductors without the presence of d-wave
superconductivity.Comment: REVTeX 3.1, 5 pages, 5 figure
Quantum coherent transport in a three-arm beam splitter and a Braess paradox
The Braess paradox encountered in classical networks is a counterintuitive
phenomenon when the flow in a road network can be impeded by adding a new road
or, more generally, the overall net performance can degrade after addition of
an extra available choice. In this work, we discuss the possibility of a
similar effect in a phase-coherent quantum transport and demonstrate it by
example of a simple Y-shaped metallic fork. To reveal the Braess-like partial
suppression of the charge flow in such device, it is proposed to transfer two
outgoing arms into a superconducting state. We show that the differential
conductance-vs-voltage spectrum of the hybrid fork structure varies
considerably when the extra link between the two superconducting leads is added
and it can serve as an indicator of quantum correlations which manifest
themselves in the quantum Braess paradox.Comment: 9 pages, 3 figures, the author version presented at the Quantum 2017
Workshop (Torino, Italy, 7-13 May 2017) and submitted to the International
Journal of Quantum Information; v2: reference 9 added and the introduction
extende
Potential Scattering in Dirac Field Theory
We develop the potential scattering of a spinor within the context of
perturbation field theory. As an application, we reproduce, up to second order
in the potential, the diffusion results for a potential barrier of quantum
mechanics. An immediate consequence is a simple generalization to arbitrary
potential forms, a feature not possible in quantum mechanics.Comment: 7 page
Dirac Equation Studies in the Tunnelling Energy Zone
We investigate the tunnelling zone V0 < E < V0+m for a one-dimensional
potential within the Dirac equation. We find the appearance of superluminal
transit times akin to the Hartman effect.Comment: 12 pages, 4 figure
WIPI1 promotes fission of endosomal transport carriers and formation of autophagosomes through distinct mechanisms.
Autophagosome formation requires PROPPIN/WIPI proteins and monophosphorylated phosphoinositides, such as phosphatidylinositol-3-phosphate (PtdIns3P) or PtdIns5P. This process occurs in association with mammalian endosomes, where the PROPPIN WIPI1 has additional, undefined roles in vesicular traffic. To explore whether these functions are interconnected, we dissected routes and subreactions of endosomal trafficking requiring WIPI1. WIPI1 specifically acts in the formation and fission of tubulo-vesicular endosomal transport carriers. This activity supports the PtdIns(3,5)P <sub>2</sub> -dependent transport of endosomal cargo toward the plasma membrane, Golgi, and lysosomes, suggesting a general role of WIPI1 in endosomal protein exit. Three features differentiate the endosomal and macroautophagic/autophagic activities of WIPI1: phosphoinositide binding site II, the requirement for PtdIns(3,5)P <sub>2</sub> , and bilayer deformation through a conserved amphipathic α-helix. Their inactivation preserves autophagy but leads to a strong enlargement of endosomes, which accumulate micrometer-long endosomal membrane tubules carrying cargo proteins. WIPI1 thus supports autophagy and protein exit from endosomes by different modes of action. We propose that the type of phosphoinositides occupying its two lipid binding sites, the most unusual feature of PROPPIN/WIPI family proteins, switches between these effector functions.Abbreviations: EGF: epidermal growth factorEGFR: epidermal growth factor receptorKD: knockdownKO: knockoutPtdIns3P: phosphatidylinositol-3-phosphatePtdIns5P: phosphatidylinositol-5-phosphatePtdIns(3,5)P <sub>2</sub> : phosphatidylinositol-3,5-bisphosphateTF: transferrinTFRC: transferrin receptorWT: wildtype
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