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Sonja Žunar

Publications and source records attributed to Sonja Žunar.

10 recordsLinked to original sources
arXiv2025

Orthogonality relations for Poincaré series

Let $ G $ be a connected semisimple Lie group with finite center. We prove a formula for the inner product of two cuspidal automorphic forms on $ G $ that are given by Poincaré series of $ K $-finite matrix coefficients of an integrable discrete series representation of $ G $. As an application, we give a new proof of a well-known result on the Petersson inner product of certain vector-valued Siegel cusp forms. In this way, we extend results previously obtained by G. Muić for cusp forms on the upper half-plane, i.e., in the case when $ G=\mathrm{SL}_2(\mathbb R) $.

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arXiv2025

On the non-vanishing of Poincaré series on irreducible bounded symmetric domains

Let $ \mathcal D\equiv G/K $ be an irreducible bounded symmetric domain. Using a vector-valued version of Muić's integral non-vanishing criterion for Poincaré series on locally compact Hausdorff groups, we study the non-vanishing of holomorphic automorphic forms on $ \mathcal D $ that are given by Poincaré series of polynomial type and correspond via the classical lift to the Poincaré series of certain $ K $-finite matrix coefficients of integrable discrete series representations of $ G $. We provide an example application of our results in the case when $ G=\mathrm{SU}(p,q) $ and $ K=\mathrm S(\mathrm U(p)\times\mathrm U(q)) $ with $ p\geq q\geq1 $.

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arXiv2024

Construction and non-vanishing of a family of vector-valued Siegel Poincaré series

Using Poincaré series of $ K $-finite matrix coefficients of integrable antiholomorphic discrete series representations of $ \mathrm{Sp}_{2n}(\mathbb R) $, we construct a spanning set for the space $ S_ρ(Γ) $ of Siegel cusp forms of weight $ ρ$ for $ Γ$, where $ ρ$ is an irreducible polynomial representation of $ \mathrm{GL}_n(\mathbb C) $ of highest weight $ ω\in\mathbb Z^n $ with $ ω_1\geq\ldots\geqω_n>2n $, and $ Γ$ is a discrete subgroup of $ \mathrm{Sp}_{2n}(\mathbb R) $ commensurable with $ \mathrm{Sp}_{2n}(\mathbb Z) $. Moreover, using a variant of Muić's integral non-vanishing criterion for Poincaré series on unimodular locally compact Hausdorff groups, we prove a result on the non-vanishing of constructed Siegel Poincaré series.

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arXiv2022

On a family of Siegel Poincaré series

Let $ Γ$ be a congruence subgroup of $ \mathrm{Sp}_{2n}(\mathbb Z) $. Using Poincaré series of $ K $-finite matrix coefficients of integrable discrete series representations of $ \mathrm{Sp}_{2n}(\mathbb R) $, we construct a spanning set for the space $ S_m(Γ) $ of Siegel cusp forms of weight $ m\in\mathbb Z_{>2n} $. We prove the non-vanishing of certain elements of this spanning set using Muić's integral non-vanishing criterion for Poincaré series on locally compact Hausdorff groups. Moreover, using the representation theory of $ \mathrm{Sp}_{2n}(\mathbb R) $, we study the Petersson inner products of corresponding cuspidal automorphic forms, thereby recovering a representation-theoretic proof of some well-known results on the reproducing kernel function of $ S_m(Γ) $. Our results are obtained by generalizing representation-theoretic methods developed by Muić in his work on holomorphic cusp forms on the upper half-plane to the setting of Siegel cusp forms of a higher degree.

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arXiv2021

On the notion of the parabolic and the cuspidal support of smooth-automorphic forms and smooth-automorphic representations

In this paper we describe several new aspects of the foundations of the representation theory of the space of smooth-automorphic forms (i.e., not necessarily $K_\infty$-finite automorphic forms) for general connected reductive groups over number fields. Our role model for this space of smooth-automorphic forms is a ''smooth version'' of the space of automorphic forms, whose internal structure was the topic of a famous paper of Franke. We prove that the important decomposition along the parabolic support, and the even finer - and structurally more important - decomposition along the cuspidal support of automorphic forms transfer in a topologized version to the larger setting of smooth-automorphic forms. In this way, we establish smooth-automorphic versions of the main results of a paper of Franke-Schwermer and of Moeglin-Waldspurger's book, III.2.6.

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arXiv2020

Non-vanishing of vector-valued Poincaré series

We prove a vector-valued version of Muić's integral non-vanishing criterion for Poincaré series on the upper half-plane $ \mathcal H $. Moreover, we give an accompanying result on the construction of vector-valued modular forms in the form of Poincaré series. As an application of these results, we construct and study the non-vanishing of the classical and elliptic vector-valued Poincaré series.

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arXiv2019

On the Schwartz space $ \mathcal S(G(k)\backslash G(\mathbb A)) $

For a connected reductive group $ G $ defined over a number field $ k $, we construct the Schwartz space $ \mathcal{S}(G(k)\backslash G(\mathbb{A})) $. This space is an adelic version of Casselman's Schwartz space $ \mathcal{S}(Γ\backslash G_\infty) $, where $ Γ$ is a discrete subgroup of $ G_\infty:=\prod_{v\in V_\infty}G(k_v) $. We study the space of tempered distributions $ \mathcal{S}(G(k)\backslash G(\mathbb A))' $ and investigate applications to automorphic forms on $ G(\mathbb A) $. In particular, we study the representation $ \left(r',\mathcal{S}(G(k)\backslash G(\mathbb{A}))'\right) $ contragredient to the right regular representation $ (r,\mathcal{S}(G(k)\backslash G(\mathbb{A}))) $ of $ G(\mathbb{A}) $ and describe the closed irreducible admissible subrepresentations of $ \mathcal{S}(G(k)\backslash G(\mathbb{A}))' $ assuming that $ G $ is semisimple.

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arXiv2017

On Poincaré series of half-integral weight

We use Poincaré series of $ K $-finite matrix coefficients of genuine integrable representations of the metaplectic cover of $ \mathrm{SL}_2(\mathbb R) $ to construct a spanning set for the space of cusp forms $ S_m(Γ,χ) $, where $ Γ$ is a discrete subgroup of finite covolume in the metaplectic cover of $ \mathrm{SL}_2(\mathbb R) $, $ χ$ is a character of $ Γ$ of finite order, and $ m\in\frac52+\mathbb Z_{\geq0} $. We give a result on the non-vanishing of the constructed cusp forms and compute their Petersson inner product with any $ f\in S_m(Γ,χ) $. Using this last result, we construct a Poincaré series $ Δ_{Γ,k,m,ξ,χ}\in S_m(Γ,χ) $ that corresponds, in the sense of the Riesz representation theorem, to the linear functional $ f\mapsto f^{(k)}(ξ) $ on $ S_m(Γ,χ) $, where $ ξ\in\mathbb C_{\Im(z)>0} $ and $ k\in\mathbb Z_{\geq0} $. Under some additional conditions on $ Γ$ and $ χ$, we provide the Fourier expansion of cusp forms $ Δ_{Γ,k,m,ξ,χ} $ and their expansion in a series of classical Poincaré series.

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arXiv2017

On the Non-Vanishing of Poincaré Series on the Metaplectic Group

In this paper, we study the $ K $-finite matrix coefficients of integrable representations of the metaplectic cover of $ \mathrm{SL}_2(\mathbb R) $ and give a result on the non-vanishing of their Poincaré series. We do this by adapting the techniques developed for $ \mathrm{SL}_2(\mathbb R) $ by Muić to the case of the metaplectic group.

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