User d_b

73 votes

Why is there a need for the concept of energy if we have the concept of momentum?

answered Oct 11, 2020 at 20:22

34 votes

Accepted

Why does the vacuum even have permeability and permittivity?

answered Nov 9, 2018 at 23:38

23 votes

Idea of Covering Group

answered Jan 31, 2014 at 3:25

22 votes

Accepted

Is the magnetic vector potential "real" in classical electromagnetism?

answered Aug 7, 2023 at 0:15

20 votes

Why is quantum gravity non-renormalizable?

answered Jun 30, 2019 at 11:57

20 votes

Why is the centre of mass of a semicircular wire outside the body?

answered Sep 30, 2020 at 20:18

15 votes

What is the physical importance of topological quantum field theory?

answered Mar 31, 2021 at 17:40

15 votes

Why does charge accumulate at points?

answered Jan 28, 2014 at 6:25

14 votes

Properties of the dot product

answered Oct 31, 2020 at 17:30

14 votes

Is this four-step recipe for quantization always valid?

answered Jul 27, 2020 at 20:31

14 votes

Is the second law of thermodynamics even a law?

answered Jul 28, 2020 at 17:07

13 votes

Is resonance a general property of second-order differential equations?

answered Feb 15, 2023 at 18:27

11 votes

Accepted

When assembling a ball of charge, why do we need less energy to assemble a bigger ball?

answered Dec 27, 2021 at 0:02

10 votes

Accepted

Proof that Vectors Describe Reality Correctly

answered Aug 13, 2020 at 19:52

10 votes

Accepted

How can (in Dirac's terminology) the product of two "real" linear operators be "not real"?

answered Mar 1, 2014 at 17:11

10 votes

Is the spacetime interval a tensor?

answered Dec 6, 2019 at 0:45

9 votes

Accepted

How entangled are the $|W\rangle$ and the $|GHZ\rangle$ states?

answered Dec 20, 2018 at 2:23

9 votes

How does potential energy increase with no work?

answered Jan 21, 2022 at 20:52

9 votes

Why is the ground warm during winter and vice-versa?

answered Sep 10, 2022 at 15:10

8 votes

Should it be 1.5K instead of 1.5°C?

answered Oct 24, 2021 at 18:34

7 votes

Accepted

Basics of photoelectric effect

answered May 25, 2022 at 19:14

7 votes

How can the electric and magnetic fields be non-zero in the absence of sources?

answered Nov 4, 2022 at 21:28

6 votes

Is $V_\text{RMS}$ an unfortunate abuse of operator?

answered Sep 26, 2022 at 20:49

6 votes

Accepted

How was the Biot-Savart law for magnetic fields derived if the Lorentz force had not been experimentally derived?

answered Jun 10, 2023 at 0:11

6 votes

Accepted

What did Feynman say about cesium chloride and body-centered cubic structure?

answered Oct 29, 2019 at 3:30

6 votes

Accepted

Is a bra-ket always a scalar?

answered Feb 21, 2019 at 23:30

5 votes

Why bulk states in quantum hall effect do not contribute to electric conductivity

answered Aug 15, 2015 at 0:02

5 votes

regarding the infinite cross section in Rutherford scattering

answered May 3, 2014 at 17:39

5 votes

Is Maxwell's field the wave function of the photon?

answered Mar 18, 2015 at 16:44

5 votes

Accepted

Question about the Lie group $SU(3) \times SU(2) \times U(1)$ and the concept of manifold

answered Sep 27, 2019 at 20:13

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192 Answers

Why is there a need for the concept of energy if we have the concept of momentum?

Why does the vacuum even have permeability and permittivity?

Idea of Covering Group

Is the magnetic vector potential "real" in classical electromagnetism?

Why is quantum gravity non-renormalizable?

Why is the centre of mass of a semicircular wire outside the body?

What is the physical importance of topological quantum field theory?

Why does charge accumulate at points?

Properties of the dot product

Is this four-step recipe for quantization always valid?

Is the second law of thermodynamics even a law?

Is resonance a general property of second-order differential equations?

When assembling a ball of charge, why do we need less energy to assemble a bigger ball?

Proof that Vectors Describe Reality Correctly

How can (in Dirac's terminology) the product of two "real" linear operators be "not real"?

Is the spacetime interval a tensor?

How entangled are the $|W\rangle$ and the $|GHZ\rangle$ states?

How does potential energy increase with no work?

Why is the ground warm during winter and vice-versa?

Should it be 1.5K instead of 1.5°C?

Basics of photoelectric effect

How can the electric and magnetic fields be non-zero in the absence of sources?

Is $V_\text{RMS}$ an unfortunate abuse of operator?

How was the Biot-Savart law for magnetic fields derived if the Lorentz force had not been experimentally derived?

What did Feynman say about cesium chloride and body-centered cubic structure?

Is a bra-ket always a scalar?

Why bulk states in quantum hall effect do not contribute to electric conductivity

regarding the infinite cross section in Rutherford scattering

Is Maxwell's field the wave function of the photon?

Question about the Lie group $SU(3) \times SU(2) \times U(1)$ and the concept of manifold