Recent content by nadia8999

in QF, every dirac delta function is accompanied by 2\pi,i.e.(2\pi)\delta(p-p_0) or (2\pi)^3\delta(\vec{p}-\vec{p_0}) the intergral element in QF is \int\frac{d^3p}{(2\pi)^3}\frac{1}{2E_P}, it comes from the integral element \int\frac{d^4p}{(2\pi)^4}(2\pi)\delta(p^2-m^2),I want to know why...

the press should be reflected in the equation, the question is what does press include. Of course it includes press from radiation and anything else? In my opinion, baryons or dusts, whatever, should have press, as far as they constitutes the gas, baryon gas or dust gas. However, the press of...

What is the criterion to determine whether they can express press or not?

The particles in the air, as we all know, are non-relativistic, but they can express press. However, I still wonder what is the criterion to determine whether they can press or not, the press of dust is 0 and why. You can refer to #8.

I agree with you, but why after recombination, the baryons do not experience pressure.

I referred to the Statistical books and found that for non-relativistic gas the press is\frac{2}{3}n \bar{\epsilon}, n is the number density and \bar{\epsilon}is the energy density. I think the baryons should be treated as gas rather than as dust.

\alpha_Bcomes from \int_0^{\infty} h \nu n(\nu)d\nu=\alpha_B T^4 so it means the average energy density of radiation. n_Bmeans the number density of bayons. Nmeans the non-relativistic particles per baryon.

In <Cosmology> written by Weinberg, in page 109, it says that \epsilon=\alpha_{B}T^4+\frac{3}{2}n_{B}Nk_{B}T p=\frac{1}{3}\alpha_{B}T^4+n_{B}Nk_{B}T \alpha_{B}T^4is the average energy density of black-body radition, then what does \frac{3}{2}n_{B}Nk_{B}Tmeans? the energy density of...