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A new method to compute the incoherent scattering function of harmonic lattices is introduced. It is based in a saddle point approximation for each term of the phonon expansion, and is simple enough to be used in practice. The method gives…

Other Condensed Matter · Physics 2018-07-20 Victor Laliena , Javier Campo

Semiclassical methods are extremely important in the subjects of wave packet and coherent state dynamics. Unfortunately, these essentially saddle point approximations are considered nearly impossible to carry out in detail for systems with…

Quantum Physics · Physics 2022-06-01 Huichao Wang , Steven Tomsovic

In this paper, we propose a variant of Riemannian stochastic recursive gradient method that can achieve second-order convergence guarantee and escape saddle points using simple perturbation. The idea is to perturb the iterates when gradient…

Optimization and Control · Mathematics 2020-10-30 Andi Han , Junbin Gao

We initiate the study of quantum algorithms for escaping from saddle points with provable guarantee. Given a function $f\colon\mathbb{R}^{n}\to\mathbb{R}$, our quantum algorithm outputs an $\epsilon$-approximate second-order stationary…

Quantum Physics · Physics 2021-08-25 Chenyi Zhang , Jiaqi Leng , Tongyang Li

The complexity of arbitrary dynamical systems and chemical reactions, in particular, can often be resolved if only the appropriate periodic orbit - in the form of a limit cycle, dividing surface, instanton trajectories or some other related…

Chemical Physics · Physics 2017-04-05 Andrej Junginger , Jörg Main , Günter Wunner , Rigoberto Hernandez

We introduce a saddle-point finder that can find the complex saddle points for any analytically continued action. We showcase our saddle-point finder by two examples in the EPRL spin foam model: the single vertex case and the case of…

General Relativity and Quantum Cosmology · Physics 2023-03-08 Zichang Huang , Shan Huang , Yidun Wan

We consider three-dimensional inviscid irrotational flow in a two layer fluid under the effects of gravity and surface tension, where the upper fluid is bounded above by a rigid lid and the lower fluid is bounded below by a flat bottom. We…

Analysis of PDEs · Mathematics 2019-07-24 Dag Nilsson

A one-parameter family of nonlinear (quartic) Klein-Gordon models having a sphaleron solution is studied. The sphaleron arises from a saddle point between true and false vacua in the energy functional. Its instability is shown be governed…

High Energy Physics - Theory · Physics 2025-10-07 Stephen C. Anco

We have studied the gradient-flow equations in information geometry from a point-particle perspective. Based on the motion of a null (or light-like) particle in a curved space, we have rederived the Hamiltonians which describe the…

Mathematical Physics · Physics 2025-08-04 Tatsuaki Wada , Antonio M. Scarfone

We develop a new semiclassical approach, which starts with the density matrix given by the Euclidean time path integral with fixed coinciding endpoints, and proceed by identifying classical (minimal Euclidean action) path, to be referred to…

High Energy Physics - Theory · Physics 2016-06-01 M. A. Escobar-Ruiz , E. Shuryak , A. V. Turbiner

Recent advancements of intermediate-scale quantum processors have triggered tremendous interest in the exploration of practical quantum advantage. The simulation of fluid dynamics, a highly challenging problem in classical physics but vital…

Gradient-based first-order convex optimization algorithms find widespread applicability in a variety of domains, including machine learning tasks. Motivated by the recent advances in fixed-time stability theory of continuous-time dynamical…

Machine Learning · Computer Science 2023-10-24 Mayank Baranwal , Param Budhraja , Vishal Raj , Ashish R. Hota

Wasserstein gradient flows on probability measures have found a host of applications in various optimization problems. They typically arise as the continuum limit of exchangeable particle systems evolving by some mean-field interaction…

Probability · Mathematics 2023-06-30 Sewoong Oh , Soumik Pal , Raghav Somani , Raghavendra Tripathi

Anisotropic particles are often encountered in different fields of soft matter and complex fluids. In this work, we present an implementation of the coupled hydrodynamics of solid ellipsoidal particles and the surrounding fluid using the…

Soft Condensed Matter · Physics 2024-06-10 Sumesh P Thampi , Kevin Stratford , Oliver Henrich

We propose a variational form of the BDF2 method as an alternative to the commonly used minimizing movement scheme for the time-discrete approximation of gradient flows in abstract metric spaces. Assuming uniform semi-convexity --- but no…

Analysis of PDEs · Mathematics 2017-12-25 Daniel Matthes , Simon Plazotta

Wasserstein gradient flow (WGF) is a common method to perform optimization over the space of probability measures. While WGF is guaranteed to converge to a first-order stationary point, for nonconvex functionals the converged solution does…

Optimization and Control · Mathematics 2025-09-23 Naoya Yamamoto , Juno Kim , Taiji Suzuki

We consider structure of typical gradient flows bifurcations on closed surfaces with minimal number of singular points. There are two type of such bifurcations: saddle-node (SN) and saddle connections (SC). The structure of a bifurcation is…

Dynamical Systems · Mathematics 2024-08-21 Illia Ovtsynov , Alexandr Prishlyak

We perform the scale setting procedure of a mixed action setup consisting of valence Wilson twisted mass fermions at maximal twist on CLS ensembles with $N_f=2+1$ flavours of $O(a)$-improved Wilson sea quarks. We determine the gradient flow…

High Energy Physics - Lattice · Physics 2024-01-25 Alejandro Saez , Alessandro Conigli , Julien Frison , Gregorio Herdoíza , Carlos Pena

A new universal theory for flow instability and turbulent transition is proposed in this study. Flow instability and turbulence transition have been challenging subjects for fluid dynamics for a century. The critical condition of turbulent…

Chaotic Dynamics · Physics 2009-09-29 Hua-Shu Dou

Several new results on the multicritical behavior of rectangular matrix models are presented. We calculate the free energy in the saddle point approximation, and show that at the triple-scaling point, the result is the same as that derived…

High Energy Physics - Theory · Physics 2010-11-01 Rene Lafrance , Robert C. Myers