45,898 research outputs found

### MAS: A versatile Landau-fluid eigenvalue code for plasma stability analysis in general geometry

We have developed a new global eigenvalue code, Multiscale Analysis for
plasma Stabilities (MAS), for studying plasma problems with wave toroidal mode
number n and frequency omega in a broad range of interest in general tokamak
geometry, based on a five-field Landau-fluid description of thermal plasmas.
Beyond keeping the necessary plasma fluid response, we further retain the
important kinetic effects including diamagnetic drift, ion finite Larmor
radius, finite parallel electric field, ion and electron Landau resonances in a
self-consistent and non-perturbative manner without sacrificing the attractive
efficiency in computation. The physical capabilities of the code are evaluated
and examined in the aspects of both theory and simulation. In theory, the
comprehensive Landau-fluid model implemented in MAS can be reduced to the
well-known ideal MHD model, electrostatic ion-fluid model, and drift-kinetic
model in various limits, which clearly delineates the physics validity regime.
In simulation, MAS has been well benchmarked with theory and other gyrokinetic
and kinetic-MHD hybrid codes in a manner of adopting the unified physical and
numerical framework, which covers the kinetic Alfven wave, ion sound wave,
low-n kink, high-n ion temperature gradient mode and kinetic ballooning mode.
Moreover, MAS is successfully applied to model the Alfven eigenmode (AE)
activities in DIII-D discharge #159243, which faithfully captures the frequency
sweeping of RSAE, the tunneling damping of TAE, as well as the polarization
characteristics of KBAE and BAAE being consistent with former gyrokinetic
theory and simulation. With respect to the key progress contributed to the
community, MAS has the advantage of combining rich physics ingredients,
realistic global geometry and high computation efficiency together for plasma
stability analysis in linear regime.Comment: 40 pages, 21 figure

### Quantum Mechanics Lecture Notes. Selected Chapters

These are extended lecture notes of the quantum mechanics course which I am
teaching in the Weizmann Institute of Science graduate physics program. They
cover the topics listed below. The first four chapter are posted here. Their
content is detailed on the next page. The other chapters are planned to be
added in the coming months.
1. Motion in External Electromagnetic Field. Gauge Fields in Quantum
Mechanics.
2. Quantum Mechanics of Electromagnetic Field
3. Photon-Matter Interactions
4. Quantization of the Schr\"odinger Field (The Second Quantization)
5. Open Systems. Density Matrix
6. Adiabatic Theory. The Berry Phase. The Born-Oppenheimer Approximation
7. Mean Field Approaches for Many Body Systems -- Fermions and Boson

### A family of total Lagrangian Petrov-Galerkin Cosserat rod finite element formulations

The standard in rod finite element formulations is the Bubnov-Galerkin
projection method, where the test functions arise from a consistent variation
of the ansatz functions. This approach becomes increasingly complex when highly
nonlinear ansatz functions are chosen to approximate the rod's centerline and
cross-section orientations. Using a Petrov-Galerkin projection method, we
propose a whole family of rod finite element formulations where the nodal
generalized virtual displacements and generalized velocities are interpolated
instead of using the consistent variations and time derivatives of the ansatz
functions. This approach leads to a significant simplification of the
expressions in the discrete virtual work functionals. In addition, independent
strategies can be chosen for interpolating the nodal centerline points and
cross-section orientations. We discuss three objective interpolation strategies
and give an in-depth analysis concerning locking and convergence behavior for
the whole family of rod finite element formulations.Comment: arXiv admin note: text overlap with arXiv:2301.0559

### Quantum resonances and analysis of the survival amplitude in the nonlinear Winter's model

In this paper we show that the typical effects of quantum resonances, namely,
the exponential-type decay of the survival amplitude, continue to exist even
when a nonlinear perturbative term is added to the time-dependent Schroedinger
equation. The difficulty in giving a rigorous and appropriate definition of
quantum resonances by means of the notions already used for linear equations is
also highlighted.Comment: 31 pages, 8 figure

### Rational-approximation-based model order reduction of Helmholtz frequency response problems with adaptive finite element snapshots

We introduce several spatially adaptive model order reduction approaches tailored to non-coercive elliptic boundary value problems, specifically, parametric-in-frequency Helmholtz problems. The offline information is computed by means of adaptive finite elements, so that each snapshot lives in a different discrete space that resolves the local singularities of the analytical solution and is adjusted to the considered frequency value. A rational surrogate is then assembled adopting either a least squares or an interpolatory approach, yielding a function-valued version of the standard rational interpolation method (V-SRI) and the minimal rational interpolation method (MRI). In the context of building an approximation for linear or quadratic functionals of the Helmholtz solution, we perform several numerical experiments to compare the proposed methodologies. Our simulations show that, for interior resonant problems (whose singularities are encoded by poles on the V-SRI and MRI work comparably well. Instead, when dealing with exterior scattering problems, whose frequency response is mostly smooth, the V-SRI method seems to be the best performing one

### Stability for the Surface Diffusion Flow

We study the global existence and stability of surface diffusion flow (the
normal velocity is given by the Laplacian of the mean curvature) of smooth
boundaries of subsets of the $n$--dimensional flat torus. More precisely, we
show that if a smooth set is ``close enough'' to a strictly stable critical set
for the Area functional under a volume constraint, then the surface diffusion
flow of its boundary hypersurface exists for all time and asymptotically
converges to the boundary of a ``translated'' of the critical set. This result
was obtained in dimension $n=3$ by Acerbi, Fusco, Julin and Morini (extending
previous results for spheres of Escher, Mayer and Simonett and Elliott and
Garcke in dimension $n=2$). Our work generalizes such conclusion to any
dimension $n\in\mathbb N$. For sake of clarity, we show all the details in
dimension $n=4$ and we list the necessary modifications to the quantities
involved in the proof in the general $n$--dimensional case, in the last
section

### Neuroanatomical and gene expression features of the rabbit accessory olfactory system. Implications of pheromone communication in reproductive behaviour and animal physiology

Mainly driven by the vomeronasal system (VNS), pheromone
communication is involved in many species-specific fundamental innate socio-sexual behaviors such as mating and
fighting, which are essential for animal reproduction and survival. Rabbits are a unique model for studying
chemocommunication due to the discovery of the rabbit mammary pheromone, but paradoxically there has been a
lack of knowledge regarding its VNS pathway. In this work, we aim at filling this gap by approaching the system
from an integrative point of view, providing extensive anatomical and genomic data of the rabbit VNS, as well as
pheromone-mediated reproductive and behavioural studies. Our results build strong foundation for further
translational studies which aim at implementing the use of pheromones to improve animal production and welfare

### Stochastic integration in Riemannian manifolds from a functional-analytic point of view

This article presents a construction of the concept of stochastic integration
in Riemannian manifolds from a purely functional-analytic point of view. We
show that there are infinitely many such integrals, and that any two of them
are related by a simple formula. We also find that the Stratonovich and It\^o
integrals known to probability theorists are two instances of the general
concept constructed herein.Comment: Minor corrections and additions. Final draft, accepted for
publication in "Journal of Functional Analysis

### Quantum Integrability vs Experiments: Correlation Functions and Dynamical Structure Factors

Integrable Quantum Field Theories can be solved exactly using bootstrap
techniques based on their elastic and factorisable S-matrix. While knowledge of
the scattering amplitudes reveals the exact spectrum of particles and their
on-shell dynamics, the expression of the matrix elements of the various
operators allows the reconstruction of off-shell quantities such as two-point
correlation functions with a high level of precision. In this review, we
summarise results relevant to the contact point between theory and experiment
providing a number of quantities that can be computed theoretically with great
accuracy. We concentrate on universal amplitude ratios which can be determined
from the measurement of generalised susceptibilities, and dynamical structure
factors, which can be accessed experimentally e.g. via inelastic neutron
scattering or nuclear magnetic resonance. Besides an overview of the subject
and a summary of recent advances, we also present new results regarding
generalised susceptibilities in the tricritical Ising universality class.Comment: 53 pages, 12 figures. arXiv admin note: text overlap with
arXiv:2109.0976

### Dispersive formalism for the nuclear structure correction $\delta_\mathrm{NS}$ to the $\beta$ decay rate

We analyze the axial $\gamma W$-box diagram for $I(J^P)=1(0^+)$ nuclei and
provide a dispersion representation of the nuclear-structure correction
$\delta_\text{NS}$ including its energy-dependent part. We also summarize
useful isospin rotation formula and representations in nuclear theory that
could facilitate the calculation of the parity-odd nuclear structure function
$F_3(\nu,Q^2)$. They provide a rigorous theory framework for the future,
high-precision calculation of the nuclear structure correction
$\delta_\text{NS}$ necessary for the extraction of the
Cabibbo-Kobayashi-Maskawa matrix element $|V_{ud}|$ from superallowed nuclear
$\beta$ decays.Comment: Version accepted by Physical Review

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