User StarBucK - Physics Stack Exchange

13 votes

3 answers

3k views

Covariance in gauge theories: why should the Lagrangian be gauge invariant?

asked Nov 25, 2017 at 15:48

11 votes

2 answers

2k views

Unstability of Fermi surface in superconductors & Cooper problem

asked Apr 16, 2017 at 14:37

10 votes

1 answer

4k views

Gupta-Bleuler and Lorenz Gauge: I don't understand the principle behind Gupta-Bleuler

asked Dec 4, 2017 at 20:40

8 votes

2 answers

3k views

Rotating wave approximation and classical Rabi oscillations: why don't the fast oscillating terms seem negligible in the initial frame?

asked Feb 3, 2019 at 16:27

8 votes

8 answers

758 views

If turning a perfectly monochromatic laser on for a finite time gives a frequency spread, where did the other frequency photons come from?

asked Jan 9, 2020 at 12:32

8 votes

1 answer

149 views

General question about quantization procedure

asked Feb 6, 2020 at 15:27

7 votes

6 answers

2k views

Very precisely explaining when phase plays a role or doesn't play a role in QM

asked Aug 16, 2020 at 16:38

7 votes

1 answer

696 views

Very basic questions about loop quantum gravity

asked May 14, 2018 at 12:28

7 votes

1 answer

1k views

Universality classes in phase transitions : how is it precisely defined?

asked Jan 11, 2018 at 16:48

7 votes

2 answers

984 views

Basic question on holomorphic formalism in QM

asked Oct 14, 2017 at 20:18

7 votes

1 answer

2k views

Density of states in $k$ space for the BCS Hamiltonian

asked Mar 5, 2017 at 15:16

6 votes

2 answers

2k views

Indistinguishable particles when wavefunctions don't overlap

asked Jan 26, 2017 at 12:47

6 votes

2 answers

709 views

Laser mode locking

asked Apr 11, 2016 at 21:12

6 votes

1 answer

1k views

Quasiparticle density of states : how to give it a meaning as the quasi particle are interacting?

asked Oct 20, 2017 at 10:11

6 votes

4 answers

448 views

PN junction: not sure to understand why reverse-biais lead to negligible current

asked Jan 6, 2021 at 14:28

6 votes

1 answer

1k views

Density of states and boundary conditions: how the density of states is physical if it depends on box size

asked May 8, 2021 at 19:37

6 votes

2 answers

338 views

Fluctuation dissipation theorem : how to identify the response variable and the force in general?

asked Apr 25, 2020 at 18:13

6 votes

1 answer

582 views

Decoherence and quantum to classical limit: good resources?

asked May 2, 2020 at 10:23

6 votes

1 answer

256 views

Validity of flat coupling approximation in input-output theory + why is it called Markov approximation?

asked May 2, 2020 at 22:12

6 votes

2 answers

2k views

Quantum input-output theory : Why do we multiply by density of mode to have a number of photon per unit of time

asked Jun 6, 2019 at 22:39

5 votes

4 answers

1k views

Why is the density of states required conceptually? Should it be seen as a mathematical trick related to Fourier series?

asked Apr 30, 2021 at 18:45

5 votes

1 answer

483 views

What is the definition of $\overleftrightarrow{\partial}$ in Dirac Lagrangian?

asked Nov 25, 2017 at 10:09

5 votes

1 answer

996 views

Why do wave vectors separated by a reciprocal lattice vector represent the same wave?

asked Sep 24, 2016 at 15:14

5 votes

2 answers

1k views

Quantization of an Hamiltonian

asked Sep 24, 2016 at 22:52

5 votes

2 answers

1k views

When can a state of the form $\rho=\sum_i p_i\lvert\psi_i\rangle\langle\psi_i\rvert$ be a pure state?

asked Dec 7, 2016 at 14:04

5 votes

1 answer

1k views

Weyl and Normal ordering in QFT

asked Apr 18, 2017 at 23:41

5 votes

2 answers

37k views

Properties of anticommutators [closed]

asked Mar 10, 2017 at 21:35

5 votes

3 answers

3k views

Klein gordon field and positive/negative energy solutions

asked Mar 25, 2017 at 20:54

5 votes

2 answers

3k views

Why my 4-divergence term added to a Lagrangian modifies the equation of motion?

asked Mar 31, 2017 at 20:29

4 votes

1 answer

3k views

Summation on nearest neighbour (Ising model for example)

asked Nov 9, 2016 at 10:54

Stack Exchange Network

227 Questions

Covariance in gauge theories: why should the Lagrangian be gauge invariant?

Unstability of Fermi surface in superconductors & Cooper problem

Gupta-Bleuler and Lorenz Gauge: I don't understand the principle behind Gupta-Bleuler

Rotating wave approximation and classical Rabi oscillations: why don't the fast oscillating terms seem negligible in the initial frame?

If turning a perfectly monochromatic laser on for a finite time gives a frequency spread, where did the other frequency photons come from?

General question about quantization procedure

Very precisely explaining when phase plays a role or doesn't play a role in QM

Very basic questions about loop quantum gravity

Universality classes in phase transitions : how is it precisely defined?

Basic question on holomorphic formalism in QM

Density of states in $k$ space for the BCS Hamiltonian

Indistinguishable particles when wavefunctions don't overlap

Laser mode locking

Quasiparticle density of states : how to give it a meaning as the quasi particle are interacting?

PN junction: not sure to understand why reverse-biais lead to negligible current

Density of states and boundary conditions: how the density of states is physical if it depends on box size

Fluctuation dissipation theorem : how to identify the response variable and the force in general?

Decoherence and quantum to classical limit: good resources?

Validity of flat coupling approximation in input-output theory + why is it called Markov approximation?

Quantum input-output theory : Why do we multiply by density of mode to have a number of photon per unit of time

Why is the density of states required conceptually? Should it be seen as a mathematical trick related to Fourier series?

What is the definition of $\overleftrightarrow{\partial}$ in Dirac Lagrangian?

Why do wave vectors separated by a reciprocal lattice vector represent the same wave?

Quantization of an Hamiltonian

When can a state of the form $\rho=\sum_i p_i\lvert\psi_i\rangle\langle\psi_i\rvert$ be a pure state?

Weyl and Normal ordering in QFT

Properties of anticommutators [closed]

Klein gordon field and positive/negative energy solutions

Why my 4-divergence term added to a Lagrangian modifies the equation of motion?

Summation on nearest neighbour (Ising model for example)