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Matrix elements are the components, or entries, of a matrix, typically considered in a certain basis.

3 votes

Pauli matrices in spherical coordinates

I'm not sure why division of matrices would be useful, or unavailable, since these matrices are all easily invertible, but you have implicitly answered your own question but failed to recognize the an …
Cosmas Zachos's user avatar
1 vote

Evaluating a matrix element of a $3\times 3$ Hamiltonian in terms of Gell-Mann matrices

You might be trapping yourself in your notation. First, appreciate that $[\lambda_\alpha,{\cal H}]= [\lambda_\alpha, H ]$, so w.l.o.g. set $h_0=0$. Moreover, since $H|n\rangle=\epsilon_n|n\rangle$, …
Cosmas Zachos's user avatar
6 votes

Generators in group theory

You really don't need to overthink it. Just do it. Note that $$ J_3^2= \operatorname {diag} ( 1,1,0) \equiv K; ~~~~J_3^3=J_3. $$ You then expand the exponential of the matrix, as normally defined, $$ …
Cosmas Zachos's user avatar
1 vote

Matrix element of two nucleon interaction

I am not sure I understand your possibly malformed question, but, ignoring the gaps, I rush to review basic facts, $$\hat{V}_{1,2}=\boldsymbol{\sigma}^{(1)}\cdot \boldsymbol{\sigma}^{(2)}= \tfrac{1}{ …
Cosmas Zachos's user avatar
2 votes

Matrix element of powers of position operator for quantum harmonic oscillator

Just to make you aware of the "bridge" expressions, the real Hermite functions (not Hermite polynomials on which they are based), $\psi_n(x)=\langle x|n\rangle$. You then have $$\langle m| \hat x ^k|n …
Cosmas Zachos's user avatar
3 votes
Accepted

SVD of $2\times 2$ matrix where entries have different units

This is a stark demonstration of the mess inflicted by failure to nondimensionalize. If your quantities are dimensional, write their units next to them, in your case: $$ M = \begin{pmatrix} 1 + xy & …
Cosmas Zachos's user avatar
0 votes
Accepted

Intrinsic $Z$-$Y$-$Z$ Euler angle sequence

Your "according to my understanding" rotation around $\hat y$, (x goes towards z when you draw the diagram, as you should), is unlike the other two, so you paved your way to dyslexia purgatory. Normal …
Cosmas Zachos's user avatar
3 votes
Accepted

Physical meaning of the rows and columns matrix representation of operators in Quantum Mecha...

Physical meaning? In simplified natural units, $$ H = {1 \over 2} (P^2 + X^2) ~, $$ is manifestly diagonal, I/2 + diag(0,1,2,3,...), for the standard matrix mechanics hermitian expressions $$ \sqrt{2 …
Cosmas Zachos's user avatar
0 votes

Non-linear sigma model quantization

If you had not resolved the constraint, e.g., of a hyperspherical O(N) model, you'd use the standard Dirack bracket procedure, not needed here. Here, you only have Goldstone scalars, and no "σ", so yo …
Cosmas Zachos's user avatar
2 votes

Matrix representation of Lorentz boost acting on a scalar

I might expedite/explain the sound answer of @Thomas Fritsch, which the comment format makes all but impossible. With due apologies to the OP, an integral kernel (propagator) which is a delta function …
Cosmas Zachos's user avatar
1 vote

Dirac Notation and Coordinate transformation of a function

I'm not sure what hack you'd be asking for in your comment to the good answer. You are meant to apply the transformation laws of the impeccable answer already provided to your scaling, (3), a change o …
Cosmas Zachos's user avatar
6 votes
Accepted

How does one calculate the position eigenvalues of the matrix corresponding to the position ...

Indirectly. To start with, set the pesky and useless constants $\hbar/m\omega \mapsto 1 $, to work in natural units. You then recognize the matrix, as Eric emphasizes by identifying to his (5), as w …
Cosmas Zachos's user avatar
2 votes
Accepted

What transformation gives a Weyl-like representation by flipping $\gamma^0$ and $\gamma^5$?

Indeed, you are doomed. There is no such V. Suppose there were an equivalence (4,5,6). Then consider $\gamma_5 = i \gamma_0 \gamma_1 \gamma_2 \gamma_3$, as well as its transform, independently of ba …
Cosmas Zachos's user avatar
5 votes
Accepted

David Hilbert's Prediction of Schrödinger Equation

As @Emilio points out, your premise is aggressively wrong. The two pictures are equivalent, and one does not dominate the other, any more than the left-hand side of an equation dominates the right-han …
Cosmas Zachos's user avatar
2 votes

Why is there an $i$ in the definition of hadronic decay constants?

Well, you may define your conventions, and physicists are perverse enough to actually do that (watch them...), any way you want. This is the dominant convention, and the logical "chain of custody", so …
Cosmas Zachos's user avatar

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