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In the variational principle leading to the Euler equation for a perfect fluid, we can use the method of undetermined multiplier for holonomic constraints representing mass conservation and adiabatic condition. For a dissipative fluid, the…

Fluid Dynamics · Physics 2012-06-03 Hiroki Fukagawa , Youhei Fujitani

In this work, we propose an Action Principle for Action-dependent Lagrangian functions by generalizing the Herglotz variational problem to the case with several independent variables. We obtain a necessary condition for the extremum…

Mathematical Physics · Physics 2018-03-23 Matheus J. Lazo , Juilson Paiva , João T. S. Amaral , Gastão S. F. Frederico

The principle of least action, a fundamental principle in variational mechanics with broad applicability to classical physical systems, is employed to formulate a novel attrition model for combat dynamics. This formulation extends the…

Physics and Society · Physics 2025-12-18 Wei Liang , Han Hu , Lijie Sun , Pingxing Chen , Ming Zhong

A simple variational Lagrangian is proposed for the time development of an arbitrary density matrix, employing the "factorization" of the density. Only the "kinetic energy" appears in the Lagrangian. The formalism applies to pure and mixed…

Fluid Dynamics · Physics 2009-11-10 R. Englman , A. Yahalom

It is shown that physical mechanics for pointlike bodies can be effectively modeled in terms of the action of transformation groups that act as symmetries of the solutions of systems of differential equations that describe the integrability…

General Relativity and Quantum Cosmology · Physics 2007-08-14 D. H. Delphenich

A variation principle for mass transport in solids is derived that recasts transport coefficients as minima of local thermodynamic average quantities. The result is independent of diffusion mechanism, and applies to amorphous and…

Statistical Mechanics · Physics 2018-12-05 Dallas R. Trinkle

The variational principle for the special and general relativistic hydrodynamics are discussed in view of its application to obtain approximate solutions to these problems. We show that effective Lagrangians can be obtained for suitable…

High Energy Physics - Phenomenology · Physics 2016-08-15 Hans-Thomas Elze , Yogiro Hama , Takeshi Kodama , Martín Makler , Johann Rafelski

We prove the existence of minimizers of causal variational principles on second countable, locally compact Hausdorff spaces. Moreover, the corresponding Euler-Lagrange equations are derived. The method is to first prove the existence of…

Mathematical Physics · Physics 2022-09-27 Felix Finster , Christoph Langer

The possibility is discussed of inferring or simulating some aspects of quantum dynamics by adding classical statistical fluctuations to classical mechanics. We introduce a general principle of mechanical stability and derive a necessary…

Quantum Physics · Physics 2015-06-26 Salvatore De Martino , Silvio De Siena , Fabrizio Illuminati

We review the development and practical uses of a generalized Maupertuis least action principle in classical mechanics, in which the action is varied under the constraint of fixed mean energy for the trial trajectory. The original…

Classical Physics · Physics 2009-11-10 C. G. Gray , G. Karl , V. A. Novikov

On the basis of a general action principle, we revisit the scale invariant field equation using the co-tensor relations by Dirac (1973). This action principle also leads to an expression for the scale factor $\lambda$, which corresponds to…

Mathematical Physics · Physics 2023-10-31 Andre Maeder , Vesselin G. Gueorguiev

We formulate a variational principle for a collection of projectors in an indefinite inner product space. The existence of minimizers is proved in various situations.

Mathematical Physics · Physics 2013-01-24 Felix Finster

The Lagrange--Poincar\'e equations for the mechanical system describing the motion of a scalar particle on a Riemannian manifold with a given free and isometric action of a compact Lie group is obtained. In an arising principle fibre…

Mathematical Physics · Physics 2014-12-31 S. N. Storchak

The first order form of a three dimensional U(1) gauge theory in which a gauge invariant mass term appears is analyzed using the Dirac procedure. The form of the gauge transformation which leaves the action invariant is derived from the…

High Energy Physics - Theory · Physics 2007-05-23 R. N. Ghalati , N. Kiriushcheva , S. V. Kuzmin , D. G. C. McKeon

The work described here shows that the known variational principle for the Navier-Stokes equations and the adjoint system can be modified to produce a set of Euler-Lagrange variational equations which have the same order and same solution…

Analysis of PDEs · Mathematics 2017-05-04 Shahrdad G. Sajjadi

We formulate a finite-size particle numerical model of strongly magnetized plasmas in the drift-kinetic approximation. We use the phase space action as an alternative to previous variational formulations based on Low's Lagrangian or on a…

Plasma Physics · Physics 2014-08-05 E. G. Evstatiev

Hydrodynamic equations for a one-component plasma are derived as a generalization of the Euler equations to include the effects of the long-range Coulomb interaction. By using a variational principle, these equations self-consistently unify…

Plasma Physics · Physics 2024-03-20 Daniels Krimans , Seth Putterman

The dynamics of particles with intrinsic angular momentum (spin) described by the Dirac equation is considered in a homogeneous space with rotation in the presence of a homogeneous vortex gravitational field. The effects of the interaction…

General Relativity and Quantum Cosmology · Physics 2024-02-20 V. G. Krechet , V. B. Oshurko , A. E. Kisser

The homogeneous causal action principle on a compact domain of momentum space is introduced. The connection to causal fermion systems is worked out. Existence and compactness results are reviewed. The Euler-Lagrange equations are derived…

Mathematical Physics · Physics 2024-07-19 Felix Finster , Michelle Frankl , Christoph Langer

We have recently presented an extension of the standard variational calculus to include the presence of deformed derivatives in the Lagrangian of a system of particles and in the Lagrangian density of field-theoretic models. Classical…

Mathematical Physics · Physics 2017-06-30 J. Weberszpil , J. A. Helayël-Neto