• Article  

      An application of homogenization theory to harmonic analysis on solvable lie groups of polynomial growth 

      Alexopoulos, Georgios K. (1993)
      Let Q be a connected solvable Lie group of polynomial growth. Let also E1, …, Ep be left invariant vector fields on G that satisfy Hοrmander’s condition and denote by L = -(E1 2 +… + Ep 2) the associated sub-Laplacian and ...
    • Article  

      Centered densities on Lie groups of polynomial volume growth 

      Alexopoulos, Georgios K. (2002)
      We study the asymptotic behavior of the convolution powers φ*n =φ*φ*⋯φ* of a centered density φ on a connected Lie group G of polynomial volume growth. The main tool is a Harnack inequality which is proved by using ideas ...
    • Article  

      Centered sub-Laplacians and densities in Lie groups of polynomial volume growth 

      Alexopoulos, Georgios K. (1998)
      We prove a Harnack inequality on connected Lie groups of polynomial volume growth. We use this inequality to study the large time behavior of the heat kernels associated to centered sub-Laplacians. Thus, we obtain Gaussian ...
    • Article  

      Convolution powers on groups of polynomial volume growth 

      Alexopoulos, Georgios K. (1997)
      We give certain estimates concerning the asymptotic behavior of convolution powers of measures on discrete groups and connected Lie groups of polynomial volume growth. We also give similar estimates for the heat kernels ...
    • Article  

      On the large time behavior of heat kernels on Lie groups 

      Lohoué, N.; Alexopoulos, Georgios K. (2003)
      We prove Gaussian estimates for heat kernels on semisimple Lie groups by using the method of Block wave representation. We also give a large time asymptotic expansion for heat kernels on compact extensions of abelian Lie groups.
    • Article  

      On the large time behavior of the heat kernels of quasiperiodic differential operators 

      Alexopoulos, Georgios K. (2000)
      We prove an analog of the Berry-Esseen estimate for the heat kernel of second order elliptic differential operators with quasiperiodic coefficients. As an application of this result, we prove the Lp boundedness of the ...
    • Article  

      Oscillating Multipliers on Lie Groups and Riemannian Manifolds 

      Alexopoulos, Georgios K. (1994)
      We prove Lpestimates for oscillating spectral multipliers on Lie groups of polynomial volume growth and Riemannian manifolds of nonnegative curvature. We apply these results to obtain Lpestimates for the Riesz means of the ...
    • Article  

      Random walks on discrete groups of polynomial volume growth 

      Alexopoulos, Georgios K. (2002)
      Let μ be a probability measure with finite support on a discrete group Γ of polynomial volume growth. The main purpose of this paper is to study the asymptotic behavior of the convolution powers μ*n μ. If μ is centered, ...
    • Article  

      Sobolev Inequalities and Harmonic Functions of Polynomial Growth 

      Alexopoulos, Georgios K.; Lohoué, N. (1993)
      We prove a Sobolev inequality for functions not necessarily with compact support, on a connected Lie group G of polynomial volume growth. To prove this inequality we have to characterise the harmonic functions of polynomial ...
    • Article  

      Spectral multipliers for Markov chains 

      Alexopoulos, Georgios K. (2004)
      We prove an analog to the classical Mikhlin-Hörmander multiplier theorem for Markov chains.
    • Article  

      Spectral multipliers on discrete groups 

      Alexopoulos, Georgios K. (2001)
      The classical Mikhlin-Hörmander multiplier theorem is generalised to the context of discrete groups of polynomial volume growth.
    • Article  

      Spectral multipliers on lie groups of polynomial growth 

      Alexopoulos, Georgios K. (1994)
      Let L be a left invariant sub-Laplacian on a connected Lie group G of polynomial volume growth, and let (Eγγ ≥ 0) be the spectral resolution of L and m a bounded Borel measurable function on [0, ∞). In this article we give ...
    • Article  

      Sub-Laplacians with drift on Lie groups of polynomial volume growth 

      Alexopoulos, Georgios K. (2002)
      We prove a parabolic Harnack inequality for a centered sub-Laplacian L on a connected Lie group G of polynomial volume growth by using ideas from Homogenisation theory and by adapting the method of Krylov and Safonov. We ...