skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Feynman path description of the effects of dephasing of spatial coherences on the transmission and reflection probabilities through a one-dimensional potential
Title: Feynman path description of the effects of dephasing of spatial coherences on the transmission and reflection probabilities through a one-dimensional potential
Abstract In this work, we examine the effects of spatial dephasing of coherences on the transmission and reflection probabilities for electrons with energyEincident to a one-dimensional rectangular barrier of heightV0. Statistical models are presented where the coherence between different scattering pathways or ‘Feynman paths’ undergo dephasing over a length scale,Lϕ. For incident waves withE>V0, three different dephasing models that attenuate the contributions of spatial coherence to the transmission and reflection probabilities while preserving unitarity (i.e., conserving charge) were investigated. In the tunneling regime (incident waves withE<V0), however, preserving unitarity requiresLϕ→ ∞ , suggesting that elastic tunneling through a rectangular barrier is 100% spatially coherent for these dephasing models. However, wave absorption models are shown to preserve unitarity in the tunneling regime, which is not the case for scattering above the barrier.  more » « less
Award ID(s):
1807724
PAR ID:
10477150
Author(s) / Creator(s):
;
Publisher / Repository:
IOP Publishing
Date Published:
Journal Name:
Physica Scripta
Volume:
98
Issue:
2
ISSN:
0031-8949
Page Range / eLocation ID:
025204
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; (, The Astrophysical Journal)
    Abstract Transport equations for electron thermal energy in the high- β e intracluster medium (ICM) are developed that include scattering from both classical collisions and self-generated whistler waves. The calculation employs an expansion of the kinetic electron equation along the ambient magnetic field in the limit of strong scattering and assumes whistler waves with low phase speeds V w ∼ v te / β e ≪ v te dominate the turbulent spectrum, with v te the electron thermal speed and β e ≫ 1 the ratio of electron thermal to magnetic pressure. We find: (1) temperature-gradient-driven whistlers dominate classical scattering when L c > L / β e , with L c the classical electron mean free path and L the electron temperature scale length, and (2) in the whistler-dominated regime the electron thermal flux is controlled by both advection at V w and a comparable diffusive term. The findings suggest whistlers limit electron heat flux over large regions of the ICM, including locations unstable to isobaric condensation. Consequences include: (1) the Field length decreases, extending the domain of thermal instability to smaller length scales, (2) the heat flux temperature dependence changes from T e 7 / 2 / L to V w nT e ∼ T e 1 / 2 , (3) the magneto-thermal- and heat-flux-driven buoyancy instabilities are impaired or completely inhibited, and (4) sound waves in the ICM propagate greater distances, as inferred from observations. This description of thermal transport can be used in macroscale ICM models. 
    more » « less
  2. ; (, Journal of Cosmology and Astroparticle Physics)
    Abstract In light of the recent swampland conjectures, we explore quantum cosmology and eternal inflation beyond the slow roll regime. We consider a model of a closed universe with a scalar field ϕ in the framework of tunneling approach to quantum cosmology. The scalar field potential is assumed to have a maximum at ϕ = 0 and can be approximated in its vicinity as V ( ϕ )≈ 3 H 2 - 1/2 m 2 ϕ 2 . Using the instanton method, we find that for m < 2 H the dominant nucleation channel for the universe is tunneling to a homogeneous, spherical de Sitter space. For larger values of m / H , the most probable tunneling is to an inhomogeneous closed universe with a domain wall wrapped around its equator. We determine the quantum state of the field ϕ in the nucleated universe by solving the Wheeler-DeWitt equation with tunneling boundary conditions. Our results agree with earlier work which assumed a slow-roll regime m ≪ H . We finally show that spherical universes nucleating with m < 2 H undergo stochastic eternal inflation with inflating regions forming a fractal of dimension d > 2. For larger values of m the field ϕ is unstable with respect to formation of domain walls and cannot be described by a perturbative stochastic approach. 
    more » « less
  3. ; (, Journal of Fluid Mechanics)
    The scattering of surface waves by structures intersecting liquid surfaces is fundamental in fluid mechanics, with prior studies exploring gravity, capillary and capillary–gravity wave interactions. This paper develops a semi-analytical framework for capillary–gravity wave scattering by a fixed, horizontally placed, semi-immersed cylindrical barrier. Assuming linearised potential flow, the problem is formulated with differential equations, conformal mapping and Fourier transforms, resulting in a compound integral equation framework solved numerically via the Nyström method. An effective-slip dynamic contact line model accounting for viscous dissipation links contact line velocity to deviations from equilibrium contact angles, with fixed and free contact lines of no dissipation as limiting cases. The framework computes transmission and reflection coefficients as functions of the Bond number, slip coefficient and barrier radius, validating energy conservation and confirming a$$90^\circ$$phase difference between transmission and reflection in specific limits. A closed-form solution for scattering by an infinitesimal barrier, derived using Fourier transforms, reveals spatial symmetry in the diffracted field, reduced transmission transitioning from gravity to capillary waves and peak contact line dissipation when the slip coefficient matches the capillary wave phase speed. This dissipation, linked to impedance matching at the contact lines, persists across a range of barrier sizes. These results advance theoretical insights into surface-tension-dominated fluid mechanics, offering a robust theoretical framework for analysing wave scattering and comparison with future experimental and numerical studies. 
    more » « less
  4. ; ; ; (, Astronomy & Astrophysics)
    Coronal mass ejections (CMEs) are often associated with X-ray (SXR) flares powered by magnetic reconnection in the low corona, while the CME shocks in the upper corona and interplanetary (IP) space accelerate electrons often producing the type II radio bursts. The CME and the reconnection event are part of the same energy release process as highlighted by the correlation between reconnection flux (ϕrec) that quantifies the strength of the released magnetic free energy during the SXR flare, and the CME kinetic energy that drives the IP shocks leading to type II bursts. Unlike the Sun, these physical parameters cannot be directly inferred in stellar observations. Hence, scaling laws between unresolved sun-as-a-star observables, namely SXR luminosity (LX) and type II luminosity (LR), and the physical properties of the associated dynamical events are crucial. Such scaling laws also provide insights into the interconnections between the particle acceleration processes across low-corona to IP space during solar-stellar “flare-CME-type II” events. Using long-term solar data in the SXR to radio waveband, we derived a scaling law between two novel power metrics for the flare and CME-associated processes. The metrics of “flare power” (Pflare = √(LXϕrec)) and “CME power” (PCME = √(LRVCME2)), whereVCMEis the CME speed, scale asPflare ∝ PCME0.76 ± 0.04. In addition,LXandϕrecshow power-law trends withPCMEwith indices of 1.12 ± 0.05 and 0.61 ± 0.05, respectively. These power laws help infer the spatially resolved physical parameters,VCMEandϕrec, from disk-averaged observables,LXandLRduring solar-stellar flare-CME-type II events. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, Nature Communications)
    Abstract Kagome vanadatesAV3Sb5display unusual low-temperature electronic properties including charge density waves (CDW), whose microscopic origin remains unsettled. Recently, CDW order has been discovered in a new material ScV6Sn6, providing an opportunity to explore whether the onset of CDW leads to unusual electronic properties. Here, we study this question using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). The ARPES measurements show minimal changes to the electronic structure after the onset of CDW. However, STM quasiparticle interference (QPI) measurements show strong dispersing features related to the CDW ordering vectors. A plausible explanation is the presence of a strong momentum-dependent scattering potential peaked at the CDW wavevector, associated with the existence of competing CDW instabilities. Our STM results further indicate that the bands most affected by the CDW are near vHS, analogous to the case ofAV3Sb5despite very different CDW wavevectors. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email