Mass dimension of a scalar field in two dimensions?

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Discussion Overview

The discussion centers on the mass dimension of a scalar field in two dimensions, particularly in the context of supersymmetry. Participants explore the implications of dimensional analysis for actions involving scalar fields and superfields, addressing both theoretical and practical aspects of constructing these actions.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant asserts that the mass dimension of a scalar field in two dimensions is 0, based on dimensional analysis of the action.
  • Another participant agrees with this assessment, confirming the mass dimension as 0 when following the same action structure as in four dimensions.
  • A subsequent participant raises a concern regarding the construction of the action for a superfield, noting that the quadratic term mentioned does not appear to be a kinetic term, which typically requires derivatives.
  • Another participant references a source that claims the term \(\bar{\phi}\phi\) is indeed the kinetic term, suggesting that integrating over \(\theta\) yields the kinetic action for the superfield components.
  • The same participant expresses confusion about the dimensions involved, particularly regarding the integration measures and the mass dimension of terms in the action, indicating potential errors in their approach.
  • There is mention of the need to consider the components of \(\theta\) and \(\bar{\theta}\) in the superfield, with an emphasis on the dimensionality of these components in two dimensions.

Areas of Agreement / Disagreement

Participants generally agree on the mass dimension of the scalar field being 0 in two dimensions, but there is disagreement regarding the nature of the quadratic term and its role as a kinetic term in the action. The discussion remains unresolved regarding the correct formulation of the action for the superfield and the associated dimensional considerations.

Contextual Notes

Participants express uncertainty about the integration measures and the dimensional analysis of terms in the action, particularly in the context of two-dimensional supersymmetry. There are unresolved questions about the implications of using different formalism and the treatment of components in the superfield.

alialice
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Which is the mass dimension of a scalar filed in 2 dimensions?
In 4 dim I know that a scalar field has mass dimension 1, by imposing that the action has dim 0:
S=\int d^4 x \partial_{\mu} A \partial^{\mu} A
where
\left[S\right]=0
\left[d^4 x \right] =-4
\left[ \partial_{\mu} \right]=1
\Rightarrow \left[A\right]=1
Doing the same in 2 dim I found
\left[A\right]=0
Is it right?
I need it for a model in supersymmetry.
 
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Yes, that's right, if you stick to the same action.
 
Ok thanks!
But now I have a problem in writing the action of the superfield
\phi =A +i \bar{\theta} \psi + \frac{i}{2}\bar{\theta} \theta F
Phi has the same mass dimension of A, 0 in two dimension.
In the kinetic part of the action, there must be a quadratic term, such as \phi \bar{\phi}, which would have mass dimension zero. But the invariants
\int d^2 x d\theta and \int d^2 x d^2 \theta
need after them something of dimension 3/2 or 1 respectively, assumed that the dimension of d\theta is 1/2 .
How can I resolve this?
 
That quadratic term you mention doesn't seem to be a kinetic term; for that you need derivatives. See e.g. chapter 4.1 of Green,Schwarz,Witten (vol.1).
 
haushofer said:
That quadratic term you mention doesn't seem to be a kinetic term; for that you need derivatives. See e.g. chapter 4.1 of Green,Schwarz,Witten (vol.1).

I'm studying on Paul West's book and at page 112 he says that \bar{\phi}\phi is the kinetic term because if you resolve the integral in theta you find the kinetic action for the component of the superfield.
I'd like to do the same thing in two dimension: writing down the action of the superfield with the kinetic term, the term with the mass and the cubic interaction term. Only in the case of cubic phi I have to resolve the integral over theta.
But my problem is the dimensions as I've just said... So I don't know what to do! Maybe I'm doing some errors?
In two dimensions theta has two components, and I don't have used the chiral formalism; in addition the components are real.
In the superfield phi, which I wrote in a my previous post, appear both theta and bar theta.
Do you have an idea of what to do? Thank you!
 

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