Recent content by navigator

I have learned the fact from Peskin QFT book,that one-particle state presents a delta function form in spectral function at s=m^2,while multiparticle states present a continuous form begin at s=4m^2,but i don't really understand the reason.What cause the difference between one-particle state and...

I am confusing following question: what is relation bewteen similarity of geometry and similar matrix (or similarity transformation). Would someone tell me something about that? Thx...

Thank for your replies.

Why do we use the term "singular" to describe singular simplex? Are there any relations between singular matrix (or singular point)and singular simplex?

Thanks. What is about this question: :-)

I have read some stuff a bit more, and learned the correspondences: radical ideal <-> variety prime ideal <-> generic point/subvariety maximal ideal <-> point spectrum <-> variety I am not quite sure whether I have repeated them correctly,and I still confuse about the questions below...

Thank you ,I think I have to spend some time to digest what your said:-)

The notion of spectrum in algebraic geometry seem to be a bit abstract to me. Is it a set of points? Is it the analogue of spectrum in Fourier transform?

Thanks for your replies. I still wonder whether we can see the image, because our eyes also act as lens during our observation and would focus the collimited light to form an image, so we would alway see an image for our eyes can focus automatically? But the fact is that when I look forward...

An object at the focal length distance from the lens is imaged at infinity,Do this mean that under this situation, our eyes could not see the image? but as our eyes could see the stars from infinity, do this mean that the image of lens which is discussed above is just viewed through screen ,and...

According to Caratheodory, the first law of thermodynamics (dE=dQ-dW) could be derived from the definition of heat (dQ=dE-dW), whether this form a circular argument or tautology ? How to clarify the confusion between the first law of thermodynamics and the definition of heat，and capture the true...

If morphism h is an extension of morphism f,we call morphism f is a restricion of morphism h; If morphism h is a lifting of morphism f,what do we call morphism f of morphism h ? Or in other words, if i is an inclusion morphism ,then what do we call the morphism f*i, as i*f is called restriction...

Funny.

Oh,the latex codes do not display properly here. So my question is what is the inverse of lifting? like restriction is the inverse of extension.

We call the function f' in this diagrams: \begin{displaymath} \begin{xy} *!C\xybox{ \xymatrix{ {E}\ar[r]^{i} \ar[d]_{f} & {X} \ar[dl]^{f'}\\ {Y} &}} \end{xy} \end{displaymath} the entension of function f; (i is an inclusion map) \begin{displaymath} \begin{xy} *!C\xybox{...