Recently I became aware of the following statement given on page 13 of this [paper][1]. First, let us recall the following definitions:

> **Definition 4.1.** Suppose $L(s)$ is an analytic $L$-function with spectral parameters $\{\mu_j\}$ and $\{\nu_k\}$. We say that $L(s)$ is ***of algebraic type*** if either every $\mu_j$ and $\nu_k$ is in $\mathbb{Z}$, or every $\mu_j$ and $\nu_k$ is in $\frac{1}{2}+\mathbb{Z}$. The integer $w_{alg}=2\max\{0,\nu_1,\dots,\nu_{d_2}\}$ is called the ***algebraic weight*** of the $L$-function.

> **Definition 4.2.** Suppose $L(s) = \sum a_n n^{-s}$ is an analytic $L$-function. We say that $L(s)$ is ***of arithmetic type*** if there exists $w_{ar}\in\mathbb{Z}$ and a number field $F$ such that $a_nn^{w_{ar}/2}\in\mathcal{O}_F$ for all $n$. The smallest such $F$ is called the ***field of coefficients***, and the smallest such $w_{ar}$ is called the ***arithmetic weight*** of the $L$-function.

The statement I am curious to know more about is the following given at the beginning of page 13 of the linked paper:

> Furthermore,
we have the ***Hodge conjecture***: $w_{alg} = w_{ar}$.

Firstly, is this the same Hodge conjecture as the usual millennium problem asking whether the dimension of the space of algebraic cycles equals the dimension of a cohomology group? If so, how does one explain this supposed connection between the usual Hodge conjecture and $L$-functions? 

My rough understanding of the equivalence between this statement and the usual way the Hodge conjecture is stated is the following:

The unresolved Hodge conjecture is about algebraic varieties and any algebraic variety $X$ does indeed have an $L$-function. The values of the $L$-function at certain points along the real axis (related to algebraic weight) appear to capture information about the dimension of cohomology groups of $X$. In contrast, the coefficients of the Dirichlet series (related to arithmetic weight) appear to capture information about algebraic subvarieties of $X$. So to say that arithmetic and algebraic weights are equal might amount to saying that the dimension of the space of algebraic cycles equals the dimension of a cohomology group?

The relationship between $w_{alg}$ and cohomology appears potentially easier to explain: for any variety, the motive computing its $k$-th cohomology has weight $k$, and hence, per the claim of the authors of the linked paper in section 4.1, the attached $L$-function will also have weight $k$. However, as far as I am aware, this says nothing about the dimension of this cohomology space, let alone the space of Hodge cycles inside of it.

For context, I became aware of this equivalence from this great YouTube [video][2], however, the relationship to the Hodge conjecture seems to also be unknown to the creator of the video, and thus I was curious to find out more as it would seem to suggest that all 3 unresolved millennium problems about pure mathematics (not considering P vs. NP) are in some way related to $L$-functions.


  [1]: https://arxiv.org/abs/1711.10375
  [2]: https://youtu.be/3fe_ZAzSExY?si=i0WnjGizTB5OKJ3A&t=1719