User ummg

6 votes

1 answer

154 views

Why is this transformation not regarded as a symmetry?

symmetry group-theory

asked May 3, 2021 at 17:42

5 votes

4 answers

316 views

How can $U$ have an arbitrary zero point and still be extensive?

asked Sep 23, 2020 at 21:13

5 votes

3 answers

244 views

Hilbert transform in soliton paper

integration complex-numbers integrable-systems analyticity solitons

asked Jan 20 at 20:48

4 votes

3 answers

138 views

Notation/convention in thermo; How is $dE = TdS - PdV$ independent of $T$ and $P$?

thermodynamics

asked Sep 2, 2020 at 18:43

3 votes

2 answers

435 views

Are Lie algebras of groups unique?

group-theory representation-theory lie-algebra

asked Jun 4, 2021 at 21:28

3 votes

2 answers

155 views

Does $S \ge 0$ follow from Callen's thermodynamic postulates?

thermodynamics entropy

asked Jul 31, 2021 at 3:22

2 votes

2 answers

95 views

Why is $d^2 U=0$ for a thermal reservoir?

thermodynamics

asked Sep 1, 2021 at 22:08

2 votes

1 answer

144 views

Carroll's Spacetime and Geometry - Notion of open subset of a manifold

general-relativity differential-geometry terminology definition topology

asked Nov 5, 2021 at 2:55

2 votes

1 answer

92 views

Details of using flat metric to raise/lower indices in linearized GR. I'm getting first order discrepancies

general-relativity metric-tensor perturbation-theory covariance linearized-theory

asked Dec 5, 2021 at 14:22

2 votes

1 answer

149 views

Killing tensor of Friedman-Robertson-Walker metric (not assuming flatness)

general-relativity cosmology metric-tensor symmetry vector-fields

asked Dec 13, 2021 at 18:40

2 votes

1 answer

53 views

Extracting $\mathbf b$ from $M = a I + \mathbf b \cdot \mathbf S$, when $S_i$ are higher spin matrices?

quantum-spin mathematical-physics group-theory representation-theory lie-algebra

asked Apr 23 at 16:00

2 votes

0 answers

75 views

Is my geometric interpretation of $T \left(\frac{\partial S}{\partial T}\right)_P = \left(\frac{\delta Q}{dT}\right)_P$ correct?

thermodynamics differential-geometry temperature entropy differentiation

asked Jul 25, 2021 at 17:14

2 votes

1 answer

112 views

$\phi$ a pseudoscalar field $\Rightarrow$ $\phi(x^0, \vec 0) = 0$?

special-relativity field-theory parity

asked Jan 28, 2021 at 3:41

2 votes

1 answer

141 views

How can the position operator be displacement invariant?

quantum-mechanics operators symmetry

asked Sep 20, 2020 at 18:00

2 votes

1 answer

479 views

Good alternatives to Georgi's Lie Algebras in Particle Physics? [duplicate]

particle-physics resource-recommendations group-theory representation-theory

asked Apr 11, 2021 at 4:09

1 vote

1 answer

62 views

$D(x)(I-P)\neq(I-P) \Rightarrow$ Not completely reducible?

group-theory representation-theory

asked Apr 11, 2021 at 4:47

1 vote

1 answer

66 views

Why am I getting this tensor rotation wrong?

tensor-calculus representation-theory

asked Apr 17, 2021 at 4:27

1 vote

0 answers

38 views

Separation into $|\Psi_{CM}\rangle$ and $|\Psi_{R}\rangle$ in abstract representation?

quantum-mechanics hilbert-space schroedinger-equation

asked Oct 20, 2020 at 19:29

1 vote

1 answer

153 views

A step in the derivation of the unitary time-evolution operator (time-ordered exponential)

quantum-field-theory operators time hamiltonian time-evolution

asked Mar 9, 2021 at 2:39

1 vote

3 answers

265 views

Covariant gradient - What am I missing?

differential-geometry coordinate-systems differentiation rotation

asked Mar 30, 2021 at 17:40

1 vote

1 answer

89 views

Is a Feynman vertex valid only if all its rotations are?

particle-physics symmetry feynman-diagrams

asked May 16, 2021 at 17:12

1 vote

1 answer

56 views

Is this the correct way to transform a trajectory between Galilean frames?

coordinate-systems inertial-frames galilean-relativity

asked May 27, 2021 at 1:03

1 vote

2 answers

86 views

Differentiation of an operator equation in paper by Chen, Lee, Pereira 1979

fluid-dynamics operators integrable-systems solitons

asked Jan 29 at 13:02

1 vote

1 answer

62 views

Abuse of notation in GR? $f(x)$ vs. $(f \circ \psi^{-1})(x)$

general-relativity differential-geometry notation

asked Nov 11, 2021 at 21:48

1 vote

1 answer

65 views

How can $p$ linearly independent vector fields span $m$-dimensional tangent space when $p>m$?

general-relativity differential-geometry

asked Nov 24, 2021 at 0:23

1 vote

1 answer

50 views

How are these two expressions for the canonical partition function equivalent?

statistical-mechanics

asked Sep 7, 2021 at 14:52

0 votes

1 answer

48 views

Derivation of dual vector component transformation. Wald's book

general-relativity differential-geometry

asked Nov 8, 2021 at 2:26

0 votes

1 answer

107 views

Does $\{\gamma^\mu,\gamma^\nu\}=2g^{\mu\nu}\mathbb1$ determine the hermiticity of the gamma matrices?

conventions dirac-equation dirac-matrices clifford-algebra

asked May 9, 2021 at 16:01

0 votes

2 answers

233 views

Since two dimensions is enough to faithfully represent $SU(2)$, how can there be irreducible representations of dimension $n>2$?

angular-momentum quantum-spin group-theory representation-theory

asked Apr 18, 2021 at 2:14

0 votes

1 answer

106 views

Confusion about group representation terminology in physics

terminology group-theory representation-theory

asked Apr 26, 2021 at 15:27

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30 Questions

Why is this transformation not regarded as a symmetry?

How can $U$ have an arbitrary zero point and still be extensive?

Hilbert transform in soliton paper

Notation/convention in thermo; How is $dE = TdS - PdV$ independent of $T$ and $P$?

Are Lie algebras of groups unique?

Does $S \ge 0$ follow from Callen's thermodynamic postulates?

Why is $d^2 U=0$ for a thermal reservoir?

Carroll's Spacetime and Geometry - Notion of open subset of a manifold

Details of using flat metric to raise/lower indices in linearized GR. I'm getting first order discrepancies

Killing tensor of Friedman-Robertson-Walker metric (not assuming flatness)

Extracting $\mathbf b$ from $M = a I + \mathbf b \cdot \mathbf S$, when $S_i$ are higher spin matrices?

Is my geometric interpretation of $T \left(\frac{\partial S}{\partial T}\right)_P = \left(\frac{\delta Q}{dT}\right)_P$ correct?

$\phi$ a pseudoscalar field $\Rightarrow$ $\phi(x^0, \vec 0) = 0$?

How can the position operator be displacement invariant?

Good alternatives to Georgi's Lie Algebras in Particle Physics? [duplicate]

$D(x)(I-P)\neq(I-P) \Rightarrow$ Not completely reducible?

Why am I getting this tensor rotation wrong?

Separation into $|\Psi_{CM}\rangle$ and $|\Psi_{R}\rangle$ in abstract representation?

A step in the derivation of the unitary time-evolution operator (time-ordered exponential)

Covariant gradient - What am I missing?

Is a Feynman vertex valid only if all its rotations are?

Is this the correct way to transform a trajectory between Galilean frames?

Differentiation of an operator equation in paper by Chen, Lee, Pereira 1979

Abuse of notation in GR? $f(x)$ vs. $(f \circ \psi^{-1})(x)$

How can $p$ linearly independent vector fields span $m$-dimensional tangent space when $p>m$?

How are these two expressions for the canonical partition function equivalent?

Derivation of dual vector component transformation. Wald's book

Does $\{\gamma^\mu,\gamma^\nu\}=2g^{\mu\nu}\mathbb1$ determine the hermiticity of the gamma matrices?

Since two dimensions is enough to faithfully represent $SU(2)$, how can there be irreducible representations of dimension $n>2$?

Confusion about group representation terminology in physics