New post in Variational-calculus

Derivation of Dirac equation using the Lagrangian density for Dirac field

June 3rd, 2020

Can we find the boundary conditions of fields from the stationary action principle?

December 12th, 2021

Why are generalized positions and generalized velocities considered as independent of each other?

August 1st, 2022

Does a four-divergence extra term in a Lagrangian density matter to the field equations?

March 13th, 2022

What's the variation of the Christoffel symbols with respect to the metric?

September 4th, 2020

Is the Lagrangian density a functional or a function?

January 17th, 2020

Functional derivative and variation of action $S$ vs Lagrangian $L$ vs Lagrangian density $\mathcal{L}$ vs Lagrangian 4-form $\mathbf{L}$

August 26th, 2020

Why is that in the action principle, the Taylor's series is limited to the first order?

August 29th, 2020

Use partial or covariant derivatives when deriving equations of a field theory?

February 2nd, 2020

How to find the Lagrangian of this system?

May 24th, 2020

Is the shorthand $ \partial_{\mu} $ strictly a partial derivative in field theory?

August 4th, 2020

How to calculate second-order variations of an action?

June 1st, 2020

Variation of the Christoffel symbols with respect to $g^{\mu\nu}$

August 12th, 2022

The derivation of fractional equations

October 21st, 2020

The dynamical variables in Lagrangian formalism

May 26th, 2020

What is the relation between (physicists) functional derivatives and Fréchet derivatives

August 26th, 2020

Introductory texts for functionals and calculus of variation

February 21st, 2020

Where can I find the full derivation of Helfrich's shape equation for closed membranes?

June 26th, 2020

Rigorous definition of the variation

March 26th, 2021

Calculus of variations -- how does it make sense to vary the position and the velocity independently?

August 1st, 2022

Variation of the metric with respect to the metric

December 13th, 2020

Rigorous underpinnings of infinitesimals in physics

September 14th, 2020

Dynamics of a rotating coin

June 29th, 2020

Derivation of Euler-Lagrange equations for Lagrangian with dependence on second order derivatives

August 1st, 2022

Why is the shape of a hanging chain not a "V"?

August 18th, 2020

Lagrangian Mechanics - Commutativity Rule $\frac{d}{dt}\delta q=\delta \frac{dq}{dt} $

August 1st, 2022

Why treat complex scalar field and its complex conjugate as two different fields?

June 25th, 2020

Given the Lagrangian density, how do I find the equations of motions for fields?

December 2nd, 2020

Understanding Derivation of Euler-Lagrange

August 31st, 2020

Why is a cycloid path the fastest way to roll a ball downward?

December 15th, 2020