Combining Riesz bases in $\mathbb R^d$

Combining Riesz bases in $R^{d}$

$Combining Riesz bases in $\mathbb R^d$ cover$

We prove that every finite union of rectangles with edges parallel to the axes in $R^{d}$ admits a Riesz basis of exponentials.

Gady Kozma, Shahaf Nitzan, Combining Riesz bases in $R^{d}$ . Rev. Mat. Iberoam. 32 (2016), no. 4, pp. 1393–1406