### Abstract

Consider an arithmetic group G(
_{OS}
) , where G is an affine group scheme with connected, simply connected absolutely almost simple generic fiber, defined over the ring of S-integers O
_{S}
of a number field K with respect to a finite set of places S. For each n∈ N, let
_{Rn}
(G(
_{OS}
)) denote the number of irreducible complex representations of G(
_{OS}
) of dimension at most n. The degree of representation growth α(G(
_{OS}
)) =
_{lim n→ ∞}
log
_{Rn}
(G(
_{OS}
)) / log n is finite if and only if G(
_{OS}
) has the weak Congruence Subgroup Property. We establish that for every G(
_{OS}
) with the weak Congruence Subgroup Property the invariant α(G(
_{OS}
)) is already determined by the absolute root system of G. To show this we demonstrate that the abscissae of convergence of the representation zeta functions of such groups are invariant under base extensions K⊂L. We deduce from our result a variant of a conjecture of Larsen and Lubotzky regarding the representation growth of irreducible lattices in higher rank semi-simple groups. In particular, this reduces Larsen and Lubotzky’s conjecture to Serre’s conjecture on the weak Congruence Subgroup Property, which it refines.

Original language | English (US) |
---|---|

Pages (from-to) | 67-135 |

Number of pages | 69 |

Journal | Geometric and Functional Analysis |

Volume | 26 |

Issue number | 1 |

DOIs | |

State | Published - Feb 1 2016 |

### Fingerprint

### ASJC Scopus subject areas

- Analysis
- Geometry and Topology

### Cite this

*Geometric and Functional Analysis*,

*26*(1), 67-135. https://doi.org/10.1007/s00039-016-0359-6

}

*Geometric and Functional Analysis*, vol. 26, no. 1, pp. 67-135. https://doi.org/10.1007/s00039-016-0359-6

**Arithmetic Groups, Base Change, and Representation Growth.** / Avni, Nir; Klopsch, Benjamin; Onn, Uri; Voll, Christopher.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Arithmetic Groups, Base Change, and Representation Growth

AU - Avni, Nir

AU - Klopsch, Benjamin

AU - Onn, Uri

AU - Voll, Christopher

PY - 2016/2/1

Y1 - 2016/2/1

N2 - Consider an arithmetic group G( OS ) , where G is an affine group scheme with connected, simply connected absolutely almost simple generic fiber, defined over the ring of S-integers O S of a number field K with respect to a finite set of places S. For each n∈ N, let Rn (G( OS )) denote the number of irreducible complex representations of G( OS ) of dimension at most n. The degree of representation growth α(G( OS )) = lim n→ ∞ log Rn (G( OS )) / log n is finite if and only if G( OS ) has the weak Congruence Subgroup Property. We establish that for every G( OS ) with the weak Congruence Subgroup Property the invariant α(G( OS )) is already determined by the absolute root system of G. To show this we demonstrate that the abscissae of convergence of the representation zeta functions of such groups are invariant under base extensions K⊂L. We deduce from our result a variant of a conjecture of Larsen and Lubotzky regarding the representation growth of irreducible lattices in higher rank semi-simple groups. In particular, this reduces Larsen and Lubotzky’s conjecture to Serre’s conjecture on the weak Congruence Subgroup Property, which it refines.

AB - Consider an arithmetic group G( OS ) , where G is an affine group scheme with connected, simply connected absolutely almost simple generic fiber, defined over the ring of S-integers O S of a number field K with respect to a finite set of places S. For each n∈ N, let Rn (G( OS )) denote the number of irreducible complex representations of G( OS ) of dimension at most n. The degree of representation growth α(G( OS )) = lim n→ ∞ log Rn (G( OS )) / log n is finite if and only if G( OS ) has the weak Congruence Subgroup Property. We establish that for every G( OS ) with the weak Congruence Subgroup Property the invariant α(G( OS )) is already determined by the absolute root system of G. To show this we demonstrate that the abscissae of convergence of the representation zeta functions of such groups are invariant under base extensions K⊂L. We deduce from our result a variant of a conjecture of Larsen and Lubotzky regarding the representation growth of irreducible lattices in higher rank semi-simple groups. In particular, this reduces Larsen and Lubotzky’s conjecture to Serre’s conjecture on the weak Congruence Subgroup Property, which it refines.

UR - http://www.scopus.com/inward/record.url?scp=84961226506&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84961226506&partnerID=8YFLogxK

U2 - 10.1007/s00039-016-0359-6

DO - 10.1007/s00039-016-0359-6

M3 - Article

AN - SCOPUS:84961226506

VL - 26

SP - 67

EP - 135

JO - Geometric and Functional Analysis

JF - Geometric and Functional Analysis

SN - 1016-443X

IS - 1

ER -