An invariant trace formula for the universal covering group of SL(2,ℝ)

Automorphic forms of arbitrary real weight can be considered as functions on the universal covering group of SL(2, ). In this situation, we prove an invariant form of the Selberg trace formula for Hecke operators. For this purpose, the Fourier transforms of weightet orbital integrals, obtained by J. Arthur, R. Herb and P. Sally, jr., are explicitly calculated. Our formula does not follow from Arthur's invariant trace formula, since the group has infinite centre, and vector-valued automorphic forms with respect to non-congruence lattices are considered.     

Proper Holomorphic Embeddings of Riemann Surfaces with Arbitrary Topology into ℂ2

We prove that given an open Riemann surface $\mathcal{N}$ of arbitrary (finite or infinite) topology, there exists an open domain $\mathcal{M}\subset \mathcal{N}$ homeomorphic to $\mathcal{N}$ which properly holomorphically embeds in ?². Furthermore, $\mathcal{M}$ can be chosen with hyperbolic conformal type. In particular, any open orientable surface M admits a complex structure $\mathcal{C}$ such that $(M,\mathcal{C})$ can be properly holomorphically embedded into ?².     

Embeddings of variable Haj?asz-Sobolev spaces into Hölder spaces of variable order

Pointwise estimates in variable exponent Sobolev spaces on quasi-metric measure spaces are investigated. Based on such estimates, Sobolev embeddings into Hölder spaces with variable order are obtained. This extends some known results to the variable exponent setting.     

New integrable systems as a limit of the elliptic SL(N, ?) top

We consider the scaling limit of an elliptic top. This limit is a combination of a scaling of the elliptic top variables, an infinite shift of the spectral parameter, and the trigonometric limit. We give general necessary constraints on the scaling of the variables and examples of such a degeneracy. A certain subclass of limit systems is integrable in the Liouville sense, which can also be shown directly.     

Zeta functions related to the group SL2(ℤ p )

An explicit formula is given for the number of subgroups of indexp ⁿ in the principle congruence subgroups of SL₂(ℤ _p ) (for odd primesp), and for the zeta function associated with the group. Asymptotically this number iscnp ⁿ , wherec is a constant depending on the congruence subgroup. Also, the zeta function of thei-th congruence subgroup coincides with the partial zeta function of the 3-generated subgroups of thei+1-th congruence subgroup, and for each indexp ⁿ the ratio between 2-generated subgroups and 3-generated subgroups tends top - 1:1, asn tends to infinity. This work is part of the author’s Ph.D. thesis carried out at the Hebrew University of Jerusalem under the supervision of Prof. A. Lubotzky. I wish to thank Prof. Lubotzky for his continual interest and encouragement without which this paper would not have been published.     

Embeddings into the Medvedev and Muchnik lattices of Π<Superscript>0</Superscript><Subscript>1</Subscript> classes

Let _w and _M be the countable distributive lattices of Muchnik and Medvedev degrees of non-empty ₁⁰ subsets of 2, under Muchnik and Medvedev reducibility, respectively. We show that all countable distributive lattices are lattice-embeddable below any non-zero element of _w. We show that many countable distributive lattices are lattice-embeddable below any non-zero element of _M.Simpsons research was partially supported by NSF Grant DMS-0070718. We thank the anonymous referee for a careful reading of this paper and helpful comments.     

Limit relation between toda chains and the elliptic SL(N, ?) top

We study a limit relation between the elliptic SL(N,?) top and Toda chains. We show that in the case of the nonautonomous SL(2, ?) top, whose equations of motion are related to the Painlevé VI equation, it turns out to be possible to modify the previously proposed procedure and in the limit obtain the nonautonomous Toda chain, whose equations of motion are equivalent to a particular case of the Painlevé III equation. We obtain the limit of the Lax pair for the elliptic SL(2, ?) top, which allows representing the equations of motion of the nonautonomous Toda chain as the equation for isomonodromic deformations.     

Smooth Embeddings of 2-Spheres in Manifolds

Ⅰ. Introduction Let g be the standard generator of H_2(CP~2;Z) and h the standard generat or of H_2(-CP;Z). It is well known that pg+qh∈H_2(CP~2#(-CP~2);Z) can be represented by a smoothly embedded 2-sphere provided |p|,|q|≤2 or ||p|-|q| ≤1, where g and h are the images of the standard generators in H_2(CP~2# (-CP~2);Z), In this paper we consider the connected sum of CP~2 and several (-Cp~2)＇s.     

The Sub-Riemannian Curvature of Curves in the Borel Subgroup of the Group SL(2,ℝ)

Mathematical Notes -     

The sails of the SL(2,ℤ) operators and their symmetries

We relate the symmetries of the hyperbolic operators of SL(2,?) to the symmetries of their sails and of the periods of their geometric continued fractions.     

Decomposition matrices of the chevalley group F4(2) and its covering group ∗

The p-decomposition matrices of the Chevalley group F₄(2) and its exceptional covering group are computed for p [d] 3,5 and 7 (up to a few unknown values for p [d] 3).     

The hypertree poset and the ℓ<Superscript>2</Superscript>-Betti numbers of the motion group of the trivial link

We give explicit formulae for the Euler characteristic and ²-cohomology of the group of motions of the trivial link, or isomorphically the group of free group automorphisms that send each standard generator to a conjugate of itself. The method is primarily combinatorial and ultimately relies on a computation of the Möbius function for the poset of labelled hypertrees.Partially supported by NSF grant no. DMS-0101506Partially supported by an AMS Centennial Research Fellowship     

Isometric Embeddings of the Spaces Θ in the Upper Half-Plane

The goal of this paper is to explain why the results concerning positive measures are significatnly differ in some cases. Bibliography: 10 titles.     

A note on dual prehomomorphisms from a group into the Margolis–Meakin expansion of a group

Semigroup Forum - We give a category-free order theoretic variant of a key result in Auinger and Szendrei (J Pure Appl Algebra 204(3):493–506, 2006) and illustrate how it might be used to...     

On the sphericity of the subgroup PSL2(ℝ) in the group of diffeomorphisms of the circle

It is shown that the group PSL₂(?) is a spherical subgroup in the group of C³-diffeomorphisms of the circle.     

Controlled algebraic K-theory of integral group ring of SL(3, ?)

We calculate the lower Controlled Algebraic K-theory of any finitely generated infinite subgroup of SL(3,Z), the group of 3×3 integral matrices of determinant 1.     

A Quasi-isometric embedding into the group of Hamiltonian diffeomorphisms with Hofer’s metric

We construct an embedding Φ of [0, 1]^∞ into Ham(M, ω), the group of Hamiltonian diffeomorphisms of a suitable closed symplectic manifold (M, ω). We then prove that Φ is in fact a quasi-isometry. After imposing further assumptions on (M, ω), we adapt our methods to construct a similar embedding of ? ⊕ [0, 1]^∞ into either Ham(M, ω) or

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, the universal cover of Ham(M, ω). Along the way, we prove results related to the filtered Floer chain complexes of radially symmetric Hamiltonians. Our proofs rely heavily on a continuity result for barcodes (as presented in [28]) associated to filtered Floer homology viewed as a persistence module.