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Wild Feather
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4 votes
3 answers
630 views

Is the parity operator an observable?

4 votes
3 answers
98 views

Why do free-falling particles converge onto the Hubble flow?

2 votes
1 answer
95 views

Why is cosmological time unique?

2 votes
1 answer
84 views

Concept of distance in cosmology

2 votes
2 answers
3k views

Expected value of linear momentum with real wave function

1 vote
1 answer
81 views

Dimensionless power spectrum

1 vote
2 answers
2k views

Variation of resistance with temperature in semiconductors

1 vote
1 answer
52 views

Different definitions of recession velocity

1 vote
2 answers
123 views

Continuity equation for the conservation of energy from the conservation of the energy-momentum tensor

1 vote
2 answers
133 views

Upper index covariant derivative $\nabla^\mu$

1 vote
1 answer
164 views

Compute density of states in momentum space and in phase space

1 vote
0 answers
51 views

Contraction of distances in explanation of relativity of simultaneity in special relativity

1 vote
1 answer
54 views

How to express symmetry of a mixed (1,1) tensor with upper and lower index?

1 vote
0 answers
32 views

Spatial and temporal derivatives of a perturbation

1 vote
0 answers
38 views

Gravitational potential for concentric spherical shells

0 votes
1 answer
30 views

Calculation about two-point correlation function in Fourier space

0 votes
1 answer
55 views

Calculating distance from the FRW metric

0 votes
1 answer
28 views

Elementary calculation of the critical density

0 votes
1 answer
39 views

Integration constant in $a(t)$ for the Einstein-de Sitter universe

0 votes
1 answer
72 views

Explanation for the value of the Hubble radius

0 votes
2 answers
63 views

Prove expression for center of mass of a curve [closed]

0 votes
1 answer
62 views

Variational method when the Hamiltonian commutes with the parity operator

0 votes
2 answers
64 views

Elementary question about the Euler-Lagrange equation

0 votes
1 answer
51 views

Elementary question about charge of doublet

0 votes
1 answer
75 views

Elementary question about Einstein notation