What is the Formula for Entries in an Nxn Hilbert Matrix?

sponsoredwalk
Messages
531
Reaction score
5
\begin{bmatrix}<br /> 1 &amp; \frac{1}{2} &amp; \frac{1}{3} \ldots &amp; \ldots &amp; \frac{1}{n}\\<br /> <br /> \frac{1}{2} &amp; \frac{1}{3} &amp; \frac{1}{4} \ldots &amp; \ldots &amp; \frac{1}{n + 1}\\<br /> <br /> \frac{1}{3} &amp; \frac{1}{4} &amp; \right \frac{1}{5}\ldots &amp; \ldots &amp; \frac{1}{n + 2}\\<br /> <br /> \vdots &amp; \vdots &amp; \vdots &amp; \ddots &amp; \vdots\\<br /> <br /> \frac{1}{n} &amp; \frac{1}{n + 1} &amp; \frac{1}{n + 2} &amp; \ldots &amp; \frac{1}{2n - 1}<br /> <br /> \end{bmatrix}


Express the individual entries h_i_jin terms of i & j.


The answer is

h_i_j = \frac{1}{i + j - 1}

but I can't for the life of me understand how you would recognize that this formula fits the pattern formed in the matrix.

If you were answering this question, would you just attempt to form a formula with n's, i's and j's floating around or is there some method that would be helpful when addressing these types of problems?
 
Physics news on Phys.org
Well, you saw that every entry was a fraction with "1" in the numerator, didn't you?:-p

So, it's just a matter of looking at the denominators.

In the first row, where i= 1, the denominators are: j=1, 1; j= 2, 2; j=3, 3; j= 4, 4; ... which are j= j+i-1.

In the second row, where i= 2, the denominators are: j= 1, 2; j= 2, 3; j= 3, 4; j= 4, 5;... which are j+ 1= j+ i- 1 again.
 
I asked online questions about Proposition 2.1.1: The answer I got is the following: I have some questions about the answer I got. When the person answering says: ##1.## Is the map ##\mathfrak{q}\mapsto \mathfrak{q} A _\mathfrak{p}## from ##A\setminus \mathfrak{p}\to A_\mathfrak{p}##? But I don't understand what the author meant for the rest of the sentence in mathematical notation: ##2.## In the next statement where the author says: How is ##A\to...
The following are taken from the two sources, 1) from this online page and the book An Introduction to Module Theory by: Ibrahim Assem, Flavio U. Coelho. In the Abelian Categories chapter in the module theory text on page 157, right after presenting IV.2.21 Definition, the authors states "Image and coimage may or may not exist, but if they do, then they are unique up to isomorphism (because so are kernels and cokernels). Also in the reference url page above, the authors present two...
When decomposing a representation ##\rho## of a finite group ##G## into irreducible representations, we can find the number of times the representation contains a particular irrep ##\rho_0## through the character inner product $$ \langle \chi, \chi_0\rangle = \frac{1}{|G|} \sum_{g\in G} \chi(g) \chi_0(g)^*$$ where ##\chi## and ##\chi_0## are the characters of ##\rho## and ##\rho_0##, respectively. Since all group elements in the same conjugacy class have the same characters, this may be...
Back
Top