The effective-action tag has no wiki summary.
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Does the ensemble of effective Lagrangians in the String theory landscape mostly include gauge theories?
String theory false vacua can be described by effective Lagrangians at low energy. Is there generally a correspondence between these effective Lagrangians and SU(N) gauge theories? Or do the effective ...
5
votes
1answer
143 views
Higher dimension operator in free Dirac Lagrangian
When discussing higher dimensional operators in a theory with fermions, why do I never see anyone ever talk about the dimension five operator $\partial_\mu\bar\psi\partial^\mu\psi$?
How does the ...
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0answers
60 views
Wilsonian vs 1PI
As a follow up to Difference between 1PI effective action and Wilsonian effective action, where can I find pedagogical material that highlights the similarities and differences between the 1PI and ...
9
votes
1answer
538 views
Self energy, 1PI, and tadpoles
I'm having a hard time reconciling the following discrepancy:
Recall that in passing to the effective action via a Legendre transformation, we interpret the effective action $\Gamma[\phi_c]$ to be ...
1
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0answers
104 views
How to show the oblique parameters S, T, and U are coefficients of d=6 operators
In Morii, Lim, Mukherjee, The Physics of the Standard Model and Beyond. 2004, ch. 8, they claim that the Peskin–Takeuchi oblique parameters S, T and U are in fact Wilson coefficients of certain ...
12
votes
1answer
92 views
6d Massive Gravity
Massive gravity (with a Fierz-Pauli mass) in 4 dimensions is very well-studied, involving exotic phenomena like the vDVZ discontinuity and the Vainshtein effect that all have an elegant and physically ...
1
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1answer
263 views
Energy, power and action
Through unit analysis, one can identify the following relationship linking energy, action and power:
$energy^2 = action \times power$
Alternatively, we rewrite this expression as:
$power = ...
17
votes
3answers
1k views
A pedestrian explanation of Renormalization Groups - from QED to classical field theories
shortly after the invention of quantum electrodynamics, one discovered that the theory had some very bad properties. It took twenty years to discover that certain infinities could be overcome by a ...
9
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2answers
633 views
Steps for going from Polyakov action to low-energy effective action (SUGRA?) in String Theory
A lot of string-theory questions have been asked here. This one is, hopefully, different in that this inquiry is specific and the expected answer would be more mathematical than philosophical in ...
