Scalar potential

About: Scalar potential is a research topic. Over the lifetime, 3642 publications have been published within this topic receiving 78868 citations. The topic is also known as: potential.

Rare region effects dominate weakly disordered three-dimensional Dirac points

Abstract: We study three-dimensional (3D) Dirac fermions with weak finite-range scalar potential disorder. In the clean system, the density of states vanishes quadratically at the Dirac point. Disorder is known to be perturbatively irrelevant, and previous theoretical work has assumed that the Dirac semimetal phase, characterized by a vanishing density of states, survives at weak disorder, with a finite disorder phase transition to a diffusive metal with a nonvanishing density of states. In this paper, we show that nonperturbative effects from rare regions, which are missed by conventional disorder-averaged calculations, instead give rise to a nonzero density of states for any nonzero disorder. Thus, there is no Dirac semimetal phase at nonzero disorder. The results are established both by a heuristic scaling argument and via a systematic saddle-point analysis. We also discuss transport near the Dirac point. At the Dirac point, we argue that transport is diffusive, and proceeds via hopping between rare resonances. As one moves in chemical potential away from the Dirac point, there are interesting intermediate-energy regimes where the rare regions produce scattering resonances that determine the dc conductivity. We derive a scaling theory of transport near disordered 3D Dirac points. We also discuss the interplay of disorder with attractive interactions at the Dirac point and the resulting granular superconducting and Bose glass phases. Our results are relevant for all 3D systems with Dirac points, including Weyl semimetals.

Exact solutions of the Klein-Gordon equation in the presence of a dyon, magnetic flux and scalar potential in the spacetime of gravitational defects

Abstract: In this paper, we analyse the relativistic quantum motion of a charged spin-0 particle in the presence of a dyon, Aharonov–Bohm magnetic field and scalar potential in the spacetimes produced by an idealized cosmic string and global monopole. In order to develop this analysis, we assume that the dyon and the Aharonov–Bohm magnetic field are superposed to both gravitational defects. Two distinct configurations for the scalar potential, S(r), are considered: (i) the potential proportional to the inverse of the radial distance, i.e. S ∝ 1/r, and (ii) the potential proportional to this distance, i.e. S ∝ r. For both cases the centre of the potentials coincides with the dyon's position. In the case of the cosmic string the Aharonov–Bohm magnetic field is considered along the defect, and for the global monopole this magnetic field pierces the defect. The energy spectra are computed for both cases and their dependence on the electrostatic and scalar coupling constants is explicitly shown. We also analyse scattering states of the Klein–Gordon equations, and show how the phase shifts depend on the geometry of the spacetime and on the coupling constants parameter.

Minkowski 3-forms, flux string vacua, axion stability and naturalness

Abstract: We discuss the role of Minkowski 3-forms in flux string vacua. In these vacua all internal closed string fluxes are in one to one correspondence with quantized Minkowski 4-forms. By performing a dimensional reduction of the D = 10 Type II supergravity actions we find that the 4-forms act as auxiliary fields of the Kahler and complex structure moduli in the effective action. We show that all the RR and NS axion dependence of the flux scalar potential appears through the said 4-forms. Gauge invariance of these forms then severely restricts the structure of the axion scalar potentials. Combined with duality symmetries it suggests that all perturbative corrections to the leading axion scalar potential V 0 should appear as an expansion in powers of V 0 itself. These facts could have an important effect e.g. on the inflaton models based on F-term axion monodromy. We also suggest that the involved multi-branched structure of string vacua provides for a new way to maintain interacting scalar masses stable against perturbative corrections.

Inflation and non-minimal scalar-curvature coupling in gravity and supergravity

Abstract: Inflationary slow-roll dynamics in Einstein gravity with a non-minimal scalar-curvature coupling can be equivalent to that in the certain f(R) gravity theory. We review the correspondence and extend it to N=1 supergravity. The non-minimal coupling in supergravity is rewritten in terms of the standard (`minimal') N=1 matter-coupled supergravity by using curved superspace. The established equivalence between two different inflationary theories means the same inflaton scalar potential, and does not imply the same post-inflationary dynamics and reheating.