# bare 'opposed to dressed' Green's function [mathematics]

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#### Noushin

##### New Member
The sentence in which I have encountered "opposed to dressed" :

" it is called the bare (as opposed to
dressed)
Green's function or sometimes it is called the effective medium. "

with thanks
Noushin

• #### Cagey

##### post mod (English Only / Latin)
Welcome to the forum, Noushin.

I assume that it is opposing the plain (bare) version to the fancy (dressed) version of something, but I can't say for certain without more context.

Could you please explain what this is about? What is Green, and what does it do? We need more context to be helpful. What we mean by context is explained here: Context and Background.

#### timpeac

##### Senior Member
Welcome to the forum, Noushin.

I assume that it is opposing the plain (bare) version to the fancy (dressed) version of something, but I can't say for certain without more context.

Could you please explain what this is about? What is Green, and what does it do? We need more context to be helpful. What we mean by context is explained here: Context and Background.
I agree with Cagey (and about the context too). "Bare" can have different meanings depending on the context and I think that the speaker is specifying that the meaning he means here is the one opposite to the word "dressed" (although quite what meaning that word itself has here is not clear without more context).

#### Noushin

##### New Member
Green's function is a function in mathematics and have many applications in physics and engineerig. almost Each differential equation that describes a physical system has a Green's function . in the context that I'm dealing with different adjectives are used whit the term "Green's function " like :

"local Green's function "
"bare Green's function "
and ,
" full Green's function "

This is the best and more descriptive sample of the context :

local green's function means a site-diagonal local in space object. If one normally works with momentum depenedent objects, it is the object you get if you sum the momentum dependent Green's functions over all momentum.

bare green's function is like a noninteracting Green's function, except it is for the impurity problem which has an additional time dependent dynamical mean field that describes it, so to avoid the confusion with
the noninteracting Green's function it is called the bare (as opposed to dressed) Green's function or ....

#### Forero

##### Senior Member
"The bare (as opposed to dressed) Green's function" = "the bare Green's function, i.e. not the/a dressed Green's function".

#### Cagey

##### post mod (English Only / Latin)
This seems to me to contain an error. It seems to me that the section I have bracketed either does not belong there, or there is something missing from it.
bare green's function is like a noninteracting Green's function, except [it is] for the impurity problem which has an additional time dependent dynamical mean field that describes it,

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