Recent content by sadraj

I think by writing Dirac equation (Relativistic counterpart of Schrödinger equation) and see it's low velocity limit , one find that spin just couples to magnetic part of the Gauge field. It is so strange that Electric field also couples to spin in low energy regime!

Mordred , The level of certainty in the theories of early universe is highly different in comparison to particle physics , condensed matter or other precise and repeatable eras of physics. Nothing bad , I do not say : Ok, stop the thinking and do not make models and theories , my opinion is that...

Chronos , But I think lack of data from early universe and moreover impossibility to repeat the experiment is a deep and important difference between early universe Cosmology and other branches of physics!

I highly recommend to read the papers of George Ellis on Multiverse and philosophical (But inevitable) aspects of current Cosmology , which often unfortunately is neglected.

bapowell , but observations of the late time universe say less than z~10 , has little information of early universe. In my opinion our trust should be more on early universe detections like gravitational waves. I really ask GOD to let us find them! :)

Another question! Why does some physicists like Hawking let themselves to say that the Cosmology(Or early universe Cosmology) has become to end! Cry!

The difference between photon and other massive particles is that the Number Operator of photons is not conserved. What is conserved is the sum of energy of the photons not their number.

Hi every body , I remember that before entering to High school I really had been loving Aerospace engineering , I had been buying all of the issues of a related magazine and thinking about how to design a Glider all over the time, sketching my designs etc.But suddenly I fell into the love of...

Hi, The point is that to write down the Lagrangian of a matter one has to specify the type of matter. The Lagrangian of a pressure-less fluid of charged particles is simply the sum of the Lagrangian of each particle. But if you want to take into account the interaction between particles ...

Hi Guys, After data release of Planck satellite , at least about early universe cosmology, nothing new except few( i.e Dipole asymmetry of the CMB temperature fluctuations ) in comparison to WMAP results was found. As a case existence of non Gaussianity at the level of squeezed limit has been...

Ok you are right! ;) I have to write precisely!

The ground state (vacuum) of the Hamiltonian corresponding to a particular field not the Hamiltonian of a harmonic oscillator.

Yeah, actually vacuums have energy , say infinite amount of energy, because the lowest energy level of quantum state of a particle ( as an example harmonic oscillator)has infinite energy. But true and false vacuum corresponds to classical fields , as an example a scalar field like Higgs can have...

bapowell , I am not sure but doesn't too low energy scale of inflation contradicts with solving horizon problem or amplitude of the power spectrum on the CMB?

For polarization data release of Planck we have to wait about 6 months! I thinks the Alan Guth point of view is that if inflation paradigm is correct , its forecast about tensor perturbation should be consistent with the data as well as scalar perturbation. This can confirm the true energy scale...