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if i want action to be positive number then it require that $\tau_i$ be bigger than $\tau_f$, isn't it true? [closed]

the action is the length of the geodesic $S=-E_o\int_i^f d\tau$ we get an action that is minimised for the correct path. if i want action to be positive number then it require that $\tau_i$ be ...
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192 views

Why lagrangian is negative number?

In the special relativistic action for a massive point particle, $$\int_{t_i}^{t_f}\mathcal {L}dt,$$ why is the Lagrangian $$\mathcal {L}=-E_o\gamma^{-1}$$ a negative number?
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Help identifying an expression for the action

I found the following expression for the action of a (free, I think) relativistic particle in my notes but I can't remember from what it came from: $$ S = \int_{0}^{N} \left [ ...
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155 views

What is the relativistic action of a massive particle?

all Lorentz observers watching a particle move will compute the same value for the quantity $$ds^2 = -(c \, dt)^2 + dx^2 + dy^2 + dz^2,$$ $$ds^2 = g_{\mu\nu}dx^{\mu}dx^{\nu},$$ and ''ds/c'' is then ...
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368 views

Deriving the action and the Lagrangian for a free particle in Relativistic mechanics

My question relates to Landau, Classical Theory of Field, Chapter 2 - Relativistic Mechanics, paragraph 8 - The principle of least action. As stated there, To determine the action integral for a ...