Graduate Towards formulating an invariant Lagrangian

Click For Summary
The discussion revolves around the formulation of an invariant Lagrangian using specific terms involving derivatives and complex coordinates. The proposed Lagrangian includes a term proportional to the derivatives of a scalar field and a complex matrix derived from the metric. A key question is whether the complex matrix can be substituted into the Lagrangian despite differences in the degrees of freedom associated with the derivatives. Participants express confusion regarding the notation and the validity of the proposed substitution, emphasizing the need for clarity on how the terms relate. The conversation highlights the complexities of manipulating Lagrangian terms in theoretical physics.
Safinaz
Messages
255
Reaction score
8
Assuming a Lagrangian proportional to the following terms:

##L \sim ( \partial_\mu \sigma) (\partial^\mu \sigma) - g^{m\bar{n}} g^{r\bar{p}} (\partial_\mu g_{mr} ) ( \partial^\mu g_{\bar{n}\bar{p}} ) ~~~~~ \to (1) ##

Where ##\mu =0,1,2,3,4## and m, n,r, p and ##\bar{n}, \bar{p}, \bar{m}## and ##\bar{r}## = 1,2,3 ( complex coordinates )

Now if I have a complex matrix

##G_{a \bar{b}} \sim g^{m\bar{n}} g^{r\bar{p}} (\partial_a g_{mr} ) ( \partial_{\bar{b}} g_{\bar{n}\bar{p}} ) ~~~~~~~~ \to (2) ##

where ##a, \bar{b}= 1, ..., h_{2,1}##and ##h_{2,1}## is an arbitrary large number.

The question now, can I sub. by ##G_{a \bar{b}}##from equ. (2) into equ. ( 1) ? with the summation on the derivatives has different degrees of freedom? Literally, can I write the Lagrangian as:

##L \sim ( \partial_\mu \sigma) (\partial^\mu \sigma) - G_{a \bar{b}} G^{a \bar{b}} ##?

Any help appreciated!
 
Physics news on Phys.org
Maybe I am misunderstanding your notation, but just ##G_{a\bar{b}}G^{a\bar{b}}## written out is not the term you are replacing in the lagrangian (even ignoring the different number of terms that would be summed), so how are you supposing this should work?
 
"Supernovae evidence for foundational change to cosmological models" https://arxiv.org/pdf/2412.15143 The paper claims: We compare the standard homogeneous cosmological model, i.e., spatially flat ΛCDM, and the timescape cosmology which invokes backreaction of inhomogeneities. Timescape, while statistically homogeneous and isotropic, departs from average Friedmann-Lemaître-Robertson-Walker evolution, and replaces dark energy by kinetic gravitational energy and its gradients, in explaining...

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 38 ·
2
Replies
38
Views
5K
  • · Replies 7 ·
Replies
7
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 25 ·
Replies
25
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K