1. CJM 2017 (vol 70 pp. 241)
 BĂ¶cherer, Siegfried; Kikuta, Toshiyuki; Takemori, Sho

Weights of the mod $p$ kernel of the theta operators
Let $\Theta ^{[j]}$ be an analogue of the Ramanujan theta operator
for Siegel modular forms.
For a given prime $p$, we give the weights of elements of mod
$p$ kernel of $\Theta ^{[j]}$,
where the mod $p$ kernel of $\Theta ^{[j]}$ is the set of all
Siegel modular forms $F$ such that $\Theta ^{[j]}(F)$ is congruent
to zero modulo $p$.
In order to construct examples of the mod $p$ kernel of $\Theta
^{[j]}$ from any Siegel modular form,
we introduce new operators $A^{(j)}(M)$ and show the modularity
of $FA^{(j)}(M)$ when $F$ is a Siegel modular form.
Finally, we give some examples of the mod $p$ kernel of $\Theta
^{[j]}$ and the filtrations of some of them.
Keywords:Siegel modular form, congruences for modular forms, Fourier coefficients, Ramanujan's operator, filtration Categories:11F33, 11F46 

2. CJM 2017 (vol 70 pp. 1076)
 Martin, Kimball

Congruences for Modular Forms mod 2 and Quaternionic $S$ideal Classes
We prove many simultaneous congruences mod 2 for elliptic and
Hilbert modular forms
among forms with different AtkinLehner eigenvalues. The proofs
involve the notion of quaternionic $S$ideal classes and the
distribution of AtkinLehner signs among
newforms.
Keywords:modular forms, congruences, quaternion algebras Categories:11F33, 11R52 
