User Qmechanic

42 votes

Accepted

Why is this translation not a linear transformation?

answered Nov 25, 2019 at 11:50

22 votes

Relation between $SU(4)$ and $SO(6)$

answered Nov 30, 2012 at 12:43

21 votes

Why is the product of two rotation matrices not commutative?

answered Nov 19, 2016 at 11:59

19 votes

Equivalence of Two Lorentz Groups $O(3,1)$ and $O(1,3)$

answered Feb 8, 2014 at 13:05

12 votes

Dirac delta function of non-linear multivariable arguments

answered Dec 27, 2013 at 10:20

12 votes

If $XYZ=ZXY$ does $e^Xe^Ye^Z=e^Ze^Xe^Y$?

answered Dec 14, 2015 at 13:37

11 votes

Accepted

An outrageous way to derive a Laurent series: why does this work?

answered Aug 13, 2014 at 15:58

9 votes

Is the exponential map to the indefinite special orthogonal groups $SO^+(p,q)$ surjective?

answered Dec 14, 2015 at 19:42

8 votes

Fourier-like expansion of a closed curve in 2D

answered Nov 18, 2011 at 23:04

8 votes

Accepted

When can the Lagrangian be squared without changing the stationary path?

answered Nov 12, 2017 at 15:38

7 votes

Why can't rotations be represented by purely imaginary quaternions?

answered Apr 22, 2022 at 15:48

7 votes

Accepted

Functional derivatives in (Physics) Field Theory

answered Oct 11, 2014 at 15:13

7 votes

Area integral over complex plane of non-holomorphic gaussian $e^{-z\bar{z}}$

answered Feb 1, 2017 at 20:50

6 votes

Unitary invariance

answered Nov 9, 2013 at 21:22

6 votes

Why is $\frac{\operatorname dy'}{\operatorname dy}$ zero, since $y'$ depends on $y$?

answered Jan 5, 2014 at 21:34

6 votes

Existence of the Pfaffian?

answered Mar 23, 2018 at 19:53

6 votes

Accepted

Functional Equation $f(x+y)-f(x-y)=2f'(x)f'(y)$

answered Aug 11, 2018 at 20:02

6 votes

Why are the fundamental and anti-fundamental representation in $\text{SL}(2,\mathbb{C})$ not equivalent?

answered Dec 5, 2018 at 12:34

6 votes

Why is this a first integral? - particle near Schwarzschild black hole

answered Apr 4, 2021 at 17:20

5 votes

Accepted

Limitation of Lagrange Multipliers

answered Dec 3, 2022 at 14:05

5 votes

What is an example of function $f: \Bbb{N} \to \Bbb{Z}$ that is a bijection?

answered Oct 10, 2014 at 0:06

5 votes

Show the Lagrange equations can also be written on Nielsen's form

answered Mar 16, 2015 at 14:05

5 votes

Geometric meaning of Berezin integration

answered Jan 29, 2018 at 20:35

5 votes

Difference between "essential boundary conditions" and "natural boundary conditions"?

answered Mar 4, 2017 at 14:15

5 votes

I have heard that $SO(3)$ is "isomorphic" to a sphere. Is this true? if so, how do we prove it?

answered Oct 26, 2018 at 5:06

5 votes

Why is the determinant of a symplectic matrix 1?

answered Mar 24, 2018 at 10:06

5 votes

Dirac delta function $\delta(f(x))$ of function $f$ with a higher-order zero

answered Nov 11, 2017 at 18:46

5 votes

Accepted

Reconstructing a functional from its Euler-Lagrange equations

answered Mar 15, 2017 at 13:18

5 votes

Euler-Lagrange-type equation for a more natural variational problem

answered Jun 11, 2020 at 10:52

5 votes

What is the geometric intuition for the $\bar \partial$-Poincare lemma, or for $\bar \partial$ more generally?

answered Sep 1, 2019 at 11:38

Stack Exchange Network

414 Answers

Why is this translation not a linear transformation?

Relation between $SU(4)$ and $SO(6)$

Why is the product of two rotation matrices not commutative?

Equivalence of Two Lorentz Groups $O(3,1)$ and $O(1,3)$

Dirac delta function of non-linear multivariable arguments

If $XYZ=ZXY$ does $e^Xe^Ye^Z=e^Ze^Xe^Y$?

An outrageous way to derive a Laurent series: why does this work?

Is the exponential map to the indefinite special orthogonal groups $SO^+(p,q)$ surjective?

Fourier-like expansion of a closed curve in 2D

When can the Lagrangian be squared without changing the stationary path?

Why can't rotations be represented by purely imaginary quaternions?

Functional derivatives in (Physics) Field Theory

Area integral over complex plane of non-holomorphic gaussian $e^{-z\bar{z}}$

Unitary invariance

Why is $\frac{\operatorname dy'}{\operatorname dy}$ zero, since $y'$ depends on $y$?

Existence of the Pfaffian?

Functional Equation $f(x+y)-f(x-y)=2f'(x)f'(y)$

Why are the fundamental and anti-fundamental representation in $\text{SL}(2,\mathbb{C})$ not equivalent?

Why is this a first integral? - particle near Schwarzschild black hole

Limitation of Lagrange Multipliers

What is an example of function $f: \Bbb{N} \to \Bbb{Z}$ that is a bijection?

Show the Lagrange equations can also be written on Nielsen's form

Geometric meaning of Berezin integration

Difference between "essential boundary conditions" and "natural boundary conditions"?

I have heard that $SO(3)$ is "isomorphic" to a sphere. Is this true? if so, how do we prove it?

Why is the determinant of a symplectic matrix 1?

Dirac delta function $\delta(f(x))$ of function $f$ with a higher-order zero

Reconstructing a functional from its Euler-Lagrange equations

Euler-Lagrange-type equation for a more natural variational problem

What is the geometric intuition for the $\bar \partial$-Poincare lemma, or for $\bar \partial$ more generally?