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Results tagged with symmetry
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user 251344
Symmetries play a big role in modern physics and have been a source of powerful tools and techniques for understanding theories and their dynamics. We say that something is symmetric if there is some transformation we can perform on that object that leaves some property unchanged. The set of symmetry transformations of an object forms a group, and the name of this group is used as the name of the symmetry of the object.
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Different derivations of first Noether's theorem [duplicate]
I'm my current studies in Noether's theorem, the two that I liked the most are joshphysics answer to this Phys SE. post, and the derivation in chapter $4$ of An Elementary Introduction to Classical Fi …
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Residual symmetry of Polyakov action in general backgrounds
the Polyakov action with background field $G_{\mu \nu}(x)$
$$S_P[X,h] = -\frac{T}{2} \int \text{d}^2 \sigma \sqrt{-h}h^{ab}\partial_a X^\mu \partial_bX^\nu G_{\mu \nu}(X) \tag1$$
there is a residual symmetry … This residual symmetry gives rise to other gauge choices. Two famous choices are the static gauge and the light-cone gauge. …
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Problem with Noether Theorem to prove that energy is conserved
Suppose an action $S = \int _{t_1}^{t_2} L(q(t),\dot{q}(t))$ that is invariant under an infinitesimal constant time translation $t \longrightarrow t' = t + \epsilon$, of course with $\epsilon = const …
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Trying to understand the conformal gauge "derivation" in Polyakov action symmetries [duplicate]
section 2.3 on p. 16 of the book "Basic Concepts of String Theory" by Blumenhagen, Lüst, Theisen, 3 symmetries of Polyakov action are discussed: Poincarè invariance, diffeomorphism invariance and weyl symmetry … If so, the condition stablished that $h_{++}=h_{--}=0$ wouldn't need an "extra symmetry"? …
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