• Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.


PO is now at the Physics Department of Bielefeld University!

New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback


(propose a free ad)

Site Statistics

205 submissions , 163 unreviewed
5,079 questions , 2,229 unanswered
5,348 answers , 22,758 comments
1,470 users with positive rep
819 active unimported users
More ...

  How to derive the effective Langrangian of matter field, say, fermi field and quasiparticle, say, spin wave?

+ 1 like - 0 dislike

In the Fermi-Hubbard model, it may lead to spin wave due to SO(3) symmetry breaking. I know how to derive the effective Lagrangian for the spin wave by integrating out the Fermi fields. However, how to derive a Lagrangian for the Fermi fields term, spin wave dynamic term and their interaction ? An example,
enter image description here

This post imported from StackExchange Physics at 2015-02-04 06:01 (UTC), posted by SE-user Xinloong Han

asked Jan 20, 2015 in Theoretical Physics by Xinloong Han (5 points) [ revision history ]
recategorized Feb 4, 2015 by Jia Yiyang
What do you mean, "derive" the Lagrangian? The Lagrangian is assumed, it is the starting point of any (well, most) QFTs, it is not derived, though one can often tell which terms may not occur through symmetry considerations.

This post imported from StackExchange Physics at 2015-02-04 06:01 (UTC), posted by SE-user ACuriousMind
I mean the effective theory. For example, starting from a Fermi Hubbard model, it may be obtain the effective model about the spin wave when one consider the spin fluctuation and integrate out the fermi field.

This post imported from StackExchange Physics at 2015-02-04 06:01 (UTC), posted by SE-user Xinloong Han

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
Please complete the anti-spam verification

user contributions licensed under cc by-sa 3.0 with attribution required

Your rights