Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)

For p∈{2,3}p\in \left\{2,3\right\} and an even integer kk, let Wk−2−(p){W}_{k-2}^{-}\left(p) be the space of period polynomials of weight k−2k-2 on Γ0+(p){\Gamma }_{0}^{+}\left(p) with eigenvalue −1-1 under the Fricke involution. We determine the dimension formula for Wk−2−(p){W}_{k-2}^{-}\left(p) a...

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Main Authors: Choi SoYoung, Kim Chang Heon, Lee Kyung Seung
Format: Article
Language:English
Published: De Gruyter 2024-12-01
Series:Open Mathematics
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Online Access:https://doi.org/10.1515/math-2024-0102
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author Choi SoYoung
Kim Chang Heon
Lee Kyung Seung
author_facet Choi SoYoung
Kim Chang Heon
Lee Kyung Seung
author_sort Choi SoYoung
collection DOAJ
description For p∈{2,3}p\in \left\{2,3\right\} and an even integer kk, let Wk−2−(p){W}_{k-2}^{-}\left(p) be the space of period polynomials of weight k−2k-2 on Γ0+(p){\Gamma }_{0}^{+}\left(p) with eigenvalue −1-1 under the Fricke involution. We determine the dimension formula for Wk−2−(p){W}_{k-2}^{-}\left(p) and construct an explicit basis for it using period functions for weakly holomorphic modular forms. Furthermore, for a quadratic form QQ, we define the function F−(z,Q){F}^{-}\left(z,Q) on the complex upper half-plane as a generating function of the cycle integrals of the canonical basis elements for the space of weakly holomorphic modular forms of weight kk and eigenvalue −1-1 under the Fricke involution on Γ0(p){\Gamma }_{0}\left(p). We also show that F−(z,Q){F}^{-}\left(z,Q) is a modular integral on Γ0+(p){\Gamma }_{0}^{+}\left(p). Our approach focuses on calculating cycle integrals within Γ0(p){\Gamma }_{0}\left(p) rather than Γ0+(p){\Gamma }_{0}^{+}\left(p), which allows us to overcome certain technical challenges. This study extends earlier work by Choi and Kim (Rational period functions and cycle integrals in higher level cases, J. Math. Anal. Appl. 427 (2015), no. 2, 741–758) which focused on eigenvalue +1, providing new insights by examining eigenvalue −1-1 cases in the theory of rational period functions and cycle integrals in this setting.
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spelling doaj-art-5ce420e5d4dc4e9b8d2daf4aaaf902062025-08-20T02:57:40ZengDe GruyterOpen Mathematics2391-54552024-12-01221476210.1515/math-2024-0102Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)Choi SoYoung0Kim Chang Heon1Lee Kyung Seung2Department of Mathematics Education and RINS, Gyeongsang National University, Jinju, Republic of KoreaDepartment of Mathematics, Sungkyunkwan University, Suwon, Republic of KoreaRINS, Gyeongsang National University, Jinju, Republic of KoreaFor p∈{2,3}p\in \left\{2,3\right\} and an even integer kk, let Wk−2−(p){W}_{k-2}^{-}\left(p) be the space of period polynomials of weight k−2k-2 on Γ0+(p){\Gamma }_{0}^{+}\left(p) with eigenvalue −1-1 under the Fricke involution. We determine the dimension formula for Wk−2−(p){W}_{k-2}^{-}\left(p) and construct an explicit basis for it using period functions for weakly holomorphic modular forms. Furthermore, for a quadratic form QQ, we define the function F−(z,Q){F}^{-}\left(z,Q) on the complex upper half-plane as a generating function of the cycle integrals of the canonical basis elements for the space of weakly holomorphic modular forms of weight kk and eigenvalue −1-1 under the Fricke involution on Γ0(p){\Gamma }_{0}\left(p). We also show that F−(z,Q){F}^{-}\left(z,Q) is a modular integral on Γ0+(p){\Gamma }_{0}^{+}\left(p). Our approach focuses on calculating cycle integrals within Γ0(p){\Gamma }_{0}\left(p) rather than Γ0+(p){\Gamma }_{0}^{+}\left(p), which allows us to overcome certain technical challenges. This study extends earlier work by Choi and Kim (Rational period functions and cycle integrals in higher level cases, J. Math. Anal. Appl. 427 (2015), no. 2, 741–758) which focused on eigenvalue +1, providing new insights by examining eigenvalue −1-1 cases in the theory of rational period functions and cycle integrals in this setting.https://doi.org/10.1515/math-2024-0102rational period functionsperiod polynomialsweakly holomorphic modular formscycle integrals11f11
spellingShingle Choi SoYoung
Kim Chang Heon
Lee Kyung Seung
Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)
Open Mathematics
rational period functions
period polynomials
weakly holomorphic modular forms
cycle integrals
11f11
title Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)
title_full Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)
title_fullStr Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)
title_full_unstemmed Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)
title_short Cycle integrals and rational period functions for Γ0+(2) and Γ0+(3)
title_sort cycle integrals and rational period functions for γ0 2 and γ0 3
topic rational period functions
period polynomials
weakly holomorphic modular forms
cycle integrals
11f11
url https://doi.org/10.1515/math-2024-0102
work_keys_str_mv AT choisoyoung cycleintegralsandrationalperiodfunctionsforg02andg03
AT kimchangheon cycleintegralsandrationalperiodfunctionsforg02andg03
AT leekyungseung cycleintegralsandrationalperiodfunctionsforg02andg03