## LOG#150. Bohr and Doctor Who: A=mc³.

The year 2013 is coming to its end…And I have a final gift for you. An impossible post! This year was the Bohr model 100th anniversary. I have talked about this subject already, here, here and here. The hydrogen spectrum is very important in … Continue reading

## LOG#149. Path integral(IV).

Final round of this thread! Approximate methods We will evaluate the path integral (PI) using an approximation known as “saddle point”. It is a semiclassical approximation sometimes referred as the method of steepest descent. Moreover, it is based on the … Continue reading

## LOG#148. Path integral (III).

Round 3! Fight… with path integrals! XD Introduction: generic aspects Consider a particle moving in one dimension (the extension to ND is trivial), the hamiltonian being of the usual form: The fundamental question and problem in the path integral (PI) … Continue reading

## LOG#147. Path integral (II).

Are you gaussian? Are you normal? My second post about the path integral will cover functional calculus, and some basic definitions, properties and formulae. What is a functional? It is a gadget that produces a number! Numbers are cool! Functions … Continue reading

## LOG#146. Path integral (I).

My next thematic thread will cover the Feynman path integral approach to Quantum Mechanics! The standard formulation of Quantum Mechanics is well known. It was built and created by Schrödinger, Heisenberg and Dirac, plus many others, between 1925-1931. Later, it … Continue reading

## LOG#145. Basic QFT in curved ST(V): the Hawking effect.

Dedicated to the warm memory of my hero as theoretical physicist S.W. Hawking. R.I.P. 1942-2018 Idea: Black Holes (BH) are “not” truly black. BH emit thermal radiation at the Hawking temperature and it is proportional to the surface gravity () … Continue reading

## LOG#144. Basic QFT in curved ST(IV): the Unruh effect.

What is the Unruh effect? Description: any accelerated observer in the traditional Minkovski state OBSERVE a thermal spectrum of particles. When we refer to the accelerated observer, usually it is called the Rindler observer in the literature as well. In … Continue reading

## LOG#143. Basic QFT in curved ST(III).

We are now ready to go back to curved spacetime in the IN/OUT formalism! We have Indeed, where when we get particles from gravity! The particle density reads For instance, in a Friedmann-Robertson-Walker metric (FRW universe) we obtain where is … Continue reading

## LOG#142. Basic QFT in curved ST(II).

I. Back to QFT in flat Spacetime. Any scalar quantum field has an action and lagrangian density: in D spacetime dimensions. The lagrangian density is usually written as follows The EOM (equation of motion) reads: A nice feynmanity! Indeed, it … Continue reading

## LOG#141. Basic QFT in curved ST(I).

This post begins a thread about Quantum Field Theory (QFT) in curved spacetime (ST). They are based on some of my notes about the subject. Enjoy it! I. LIMITS FROM QUANTUM MECHANICS AND GENERAL RELATIVITY. The Einstein-Hilbert action in General … Continue reading