[{"language":[{"iso":"eng"}],"_id":"65073","user_id":"100325","author":[{"id":"100325","last_name":"Papageorgiou","first_name":"Efthymia","full_name":"Papageorgiou, Efthymia"}],"year":"2026","status":"public","title":"Long-time asymptotics for the heat kernel and for heat equation solutions on homogeneous trees","date_updated":"2026-07-03T12:30:49Z","date_created":"2026-03-20T17:55:24Z","external_id":{"arxiv":["2603.11232"]},"type":"preprint","citation":{"mla":"Papageorgiou, Efthymia. “Long-Time Asymptotics for the Heat Kernel and for Heat Equation Solutions on Homogeneous Trees.” 2603.11232, 2026.","ama":"Papageorgiou E. Long-time asymptotics for the heat kernel and for heat equation solutions on homogeneous trees. 260311232. Published online 2026.","bibtex":"@article{Papageorgiou_2026, title={Long-time asymptotics for the heat kernel and for heat equation solutions on homogeneous trees}, journal={2603.11232}, author={Papageorgiou, Efthymia}, year={2026} }","apa":"Papageorgiou, E. (2026). Long-time asymptotics for the heat kernel and for heat equation solutions on homogeneous trees. In 2603.11232.","ieee":"E. Papageorgiou, “Long-time asymptotics for the heat kernel and for heat equation solutions on homogeneous trees,” 2603.11232. 2026.","chicago":"Papageorgiou, Efthymia. “Long-Time Asymptotics for the Heat Kernel and for Heat Equation Solutions on Homogeneous Trees.” 2603.11232, 2026.","short":"E. Papageorgiou, 2603.11232 (2026)."},"publication":"2603.11232","project":[{"_id":"357","name":"TRR 358: Ganzzahlige Strukturen in Geometrie und Darstellungstheorie"}],"abstract":[{"lang":"eng","text":"We study the large-time behavior of the continuous-time heat kernel and of solutions to the heat equation on homogeneous trees. First, we derive sharp asymptotic formulas for the heat kernel as $t\\to\\infty$. Second, using them, we show that solutions with initial data in weighted $\\ell^1$ classes, asymptotically factorize in $\\ell^p$ norms, $p\\in[1,\\infty]$, as the product of the heat kernel, times a $p$-mass function, dependent on the initial condition and $p$. The $p$-mass function is described in terms of boundary averages associated with Busemann functions for $p<2$, while for $p\\ge 2$, it is expressed through convolution with the ground spherical function. For comparison, the case of the integers shows that a single constant mass determines the asymptotics of solutions to the heat equation for all $p$, emphasizing the influence of the graph geometry on heat diffusion."}]},{"citation":{"chicago":"Chalmoukis, Nikolaos, Stefano Meda, Efthymia Papageorgiou, and Federico Santagati. “Uncentred Maximal Operators with Respect to Half Balls on Damek--Ricci Spaces.” ArXiv:2604.27839, 2026.","short":"N. Chalmoukis, S. Meda, E. Papageorgiou, F. Santagati, ArXiv:2604.27839 (2026).","apa":"Chalmoukis, N., Meda, S., Papageorgiou, E., & Santagati, F. (2026). Uncentred maximal operators with respect to half balls on Damek--Ricci spaces. In arXiv:2604.27839.","ieee":"N. Chalmoukis, S. Meda, E. Papageorgiou, and F. Santagati, “Uncentred maximal operators with respect to half balls on Damek--Ricci spaces,” arXiv:2604.27839. 2026.","ama":"Chalmoukis N, Meda S, Papageorgiou E, Santagati F. Uncentred maximal operators with respect to half balls on Damek--Ricci spaces. arXiv:260427839. Published online 2026.","bibtex":"@article{Chalmoukis_Meda_Papageorgiou_Santagati_2026, title={Uncentred maximal operators with respect to half balls on Damek--Ricci spaces}, journal={arXiv:2604.27839}, author={Chalmoukis, Nikolaos and Meda, Stefano and Papageorgiou, Efthymia and Santagati, Federico}, year={2026} }","mla":"Chalmoukis, Nikolaos, et al. “Uncentred Maximal Operators with Respect to Half Balls on Damek--Ricci Spaces.” ArXiv:2604.27839, 2026."},"publication":"arXiv:2604.27839","project":[{"name":"TRR 358: Ganzzahlige Strukturen in Geometrie und Darstellungstheorie","_id":"357"}],"abstract":[{"lang":"eng","text":"In this paper we study a variant of the uncentred Hardy--Littlewood maximal operator on Damek--Ricci spaces in which balls are replaced by suitable half balls. Perhaps surprisingly, such modified maximal operator has better boundedness properties than the classical one. In particular, it satisfies an $L\\log L$ endpoint estimate and it is bounded on $L^p$ for every $p$ in $(1,\\infty]$."}],"date_created":"2026-05-03T19:27:27Z","external_id":{"arxiv":["2604.27839"]},"type":"preprint","author":[{"first_name":"Nikolaos","last_name":"Chalmoukis","full_name":"Chalmoukis, Nikolaos"},{"last_name":"Meda","first_name":"Stefano","full_name":"Meda, Stefano"},{"id":"100325","full_name":"Papageorgiou, Efthymia","last_name":"Papageorgiou","first_name":"Efthymia"},{"first_name":"Federico","last_name":"Santagati","full_name":"Santagati, Federico"}],"year":"2026","title":"Uncentred maximal operators with respect to half balls on Damek--Ricci spaces","status":"public","date_updated":"2026-07-03T12:30:33Z","language":[{"iso":"eng"}],"_id":"65546","user_id":"100325"},{"project":[{"_id":"357","name":"TRR 358: Ganzzahlige Strukturen in Geometrie und Darstellungstheorie"}],"citation":{"chicago":"Papageorgiou, Efthymia, and Bartosz Trojan. “Mass Functions and Asymptotic Behavior of Caloric Functions on Affine Buildings.” Mathematische Annalen 395, no. 30 (2026).","short":"E. Papageorgiou, B. Trojan, Mathematische Annalen 395 (2026).","apa":"Papageorgiou, E., & Trojan, B. (2026). Mass Functions and Asymptotic Behavior of Caloric Functions on Affine Buildings. Mathematische Annalen, 395(30).","ieee":"E. Papageorgiou and B. Trojan, “Mass Functions and Asymptotic Behavior of Caloric Functions on Affine Buildings,” Mathematische Annalen, vol. 395, no. 30, 2026.","ama":"Papageorgiou E, Trojan B. Mass Functions and Asymptotic Behavior of Caloric Functions on Affine Buildings. Mathematische Annalen. 2026;395(30).","bibtex":"@article{Papageorgiou_Trojan_2026, title={Mass Functions and Asymptotic Behavior of Caloric Functions on Affine Buildings}, volume={395}, number={30}, journal={Mathematische Annalen}, author={Papageorgiou, Efthymia and Trojan, Bartosz}, year={2026} }","mla":"Papageorgiou, Efthymia, and Bartosz Trojan. “Mass Functions and Asymptotic Behavior of Caloric Functions on Affine Buildings.” Mathematische Annalen, vol. 395, no. 30, 2026."},"issue":"30","publication":"Mathematische Annalen","type":"journal_article","date_created":"2026-02-19T11:41:25Z","external_id":{"unknown":["ttps://doi.org/10.1007/s00208-026-03453-1"]},"intvolume":" 395","date_updated":"2026-07-03T12:36:36Z","author":[{"id":"100325","first_name":"Efthymia","last_name":"Papageorgiou","full_name":"Papageorgiou, Efthymia"},{"full_name":"Trojan, Bartosz","last_name":"Trojan","first_name":"Bartosz"}],"status":"public","year":"2026","title":"Mass Functions and Asymptotic Behavior of Caloric Functions on Affine Buildings","volume":395,"user_id":"100325","language":[{"iso":"eng"}],"_id":"64266"},{"article_number":"rnaf074","language":[{"iso":"eng"}],"doi":"10.1093/imrn/rnaf074","year":"2025","title":"L p Asymptotics for the Heat Equation on Symmetric Spaces for Non-symmetric Solutions","publication_identifier":{"issn":["1073-7928","1687-0247"]},"author":[{"id":"100325","full_name":"Papageorgiou, Efthymia","first_name":"Efthymia","last_name":"Papageorgiou"}],"date_updated":"2026-07-03T12:36:03Z","publication_status":"published","intvolume":" 2025","date_created":"2026-01-06T09:45:00Z","type":"journal_article","publication":"International Mathematics Research Notices","issue":"7","abstract":[{"lang":"eng","text":"Abstract\r\n The main goal of this work is to study the $L^{p}$-asymptotic behavior of solutions to the heat equation on arbitrary rank Riemannian symmetric spaces of non-compact-type $G/K$ for non-bi-$K$ invariant initial data. For initial data $u_{0}$ compactly supported or in a weighted $L^{1}(G/K)$ space with a weight depending on $p\\in [1, \\infty ]$, we introduce a mass function $M_{p}(u_{0})(\\cdot )$, and prove that if $h_{t}$ is the heat kernel on $G/K$, then $$ \\begin{align*} &\\|h_t\\|_p^{-1}\\,\\|u_0\\ast h_t \\, - \\,M_p(u_0)(\\cdot)\\,h_t\\|_p \\rightarrow 0 \\quad \\textrm{as} \\quad t\\rightarrow \\infty.\\end{align*} $$ Interestingly, the $L^{p}$ heat concentration leads to completely different expressions of the mass function for $1\\leq p <2$ and $2\\leq p\\leq \\infty $. If we further assume that the initial data are bi-$K$-invariant, then our mass function boils down to the constant $\\int _{G/K}u_{0}$ in the case $p=1$, and more generally to $\\mathcal{H}{u_{0}}(i\\rho (2/p-1))$ if $1\\leq p<2$, and to $\\mathcal{H}{u_{0}}(0)$ if $2\\leq p \\leq \\infty $. Thus, we improve upon results by Vázquez, Anker et al., and Naik et al., clarifying the nature of the problem."}],"_id":"63505","publisher":"Oxford University Press (OUP)","user_id":"100325","volume":2025,"status":"public","citation":{"apa":"Papageorgiou, E. (2025). L p Asymptotics for the Heat Equation on Symmetric Spaces for Non-symmetric Solutions. International Mathematics Research Notices, 2025(7), Article rnaf074. https://doi.org/10.1093/imrn/rnaf074","ieee":"E. Papageorgiou, “L p Asymptotics for the Heat Equation on Symmetric Spaces for Non-symmetric Solutions,” International Mathematics Research Notices, vol. 2025, no. 7, Art. no. rnaf074, 2025, doi: 10.1093/imrn/rnaf074.","chicago":"Papageorgiou, Efthymia. “L p Asymptotics for the Heat Equation on Symmetric Spaces for Non-Symmetric Solutions.” International Mathematics Research Notices 2025, no. 7 (2025). https://doi.org/10.1093/imrn/rnaf074.","short":"E. Papageorgiou, International Mathematics Research Notices 2025 (2025).","mla":"Papageorgiou, Efthymia. “L p Asymptotics for the Heat Equation on Symmetric Spaces for Non-Symmetric Solutions.” International Mathematics Research Notices, vol. 2025, no. 7, rnaf074, Oxford University Press (OUP), 2025, doi:10.1093/imrn/rnaf074.","ama":"Papageorgiou E. L p Asymptotics for the Heat Equation on Symmetric Spaces for Non-symmetric Solutions. International Mathematics Research Notices. 2025;2025(7). doi:10.1093/imrn/rnaf074","bibtex":"@article{Papageorgiou_2025, title={L p Asymptotics for the Heat Equation on Symmetric Spaces for Non-symmetric Solutions}, volume={2025}, DOI={10.1093/imrn/rnaf074}, number={7rnaf074}, journal={International Mathematics Research Notices}, publisher={Oxford University Press (OUP)}, author={Papageorgiou, Efthymia}, year={2025} }"}},{"publication":"arXiv:2509.12349","citation":{"mla":"Bruno, Tommaso, and Efthymia Papageorgiou. “Blow-up Exponents and a Semilinear Elliptic Equation for the Fractional Laplacian on Hyperbolic Spaces.” ArXiv:2509.12349, 2025.","ama":"Bruno T, Papageorgiou E. Blow-up exponents and a semilinear elliptic equation for the fractional Laplacian on hyperbolic spaces. arXiv:250912349. Published online 2025.","bibtex":"@article{Bruno_Papageorgiou_2025, title={Blow-up exponents and a semilinear elliptic equation for the fractional Laplacian on hyperbolic spaces}, journal={arXiv:2509.12349}, author={Bruno, Tommaso and Papageorgiou, Efthymia}, year={2025} }","apa":"Bruno, T., & Papageorgiou, E. (2025). Blow-up exponents and a semilinear elliptic equation for the fractional Laplacian on hyperbolic spaces. In arXiv:2509.12349.","ieee":"T. Bruno and E. Papageorgiou, “Blow-up exponents and a semilinear elliptic equation for the fractional Laplacian on hyperbolic spaces,” arXiv:2509.12349. 2025.","short":"T. Bruno, E. Papageorgiou, ArXiv:2509.12349 (2025).","chicago":"Bruno, Tommaso, and Efthymia Papageorgiou. “Blow-up Exponents and a Semilinear Elliptic Equation for the Fractional Laplacian on Hyperbolic Spaces.” ArXiv:2509.12349, 2025."},"abstract":[{"text":"Let $\\mathbb{H}^n$ be the $n$-dimensional real hyperbolic space, $Δ$ its nonnegative Laplace--Beltrami operator whose bottom of the spectrum we denote by $λ_{0}$, and $σ\\in (0,1)$.\r\n The aim of this paper is twofold. On the one hand, we determine the Fujita exponent for the fractional heat equation \\[\\partial_{t} u + Δ^σu = e^{βt}|u|^{γ-1}u,\\] by proving that nontrivial positive global solutions exist if and only if $γ\\geq 1 + β/ λ_{0}^σ$. On the other hand, we prove the existence of non-negative, bounded and finite energy solutions of the semilinear fractional elliptic equation \\[\r\n Δ^σ v - λ^σ v - v^γ=0 \\] for $0\\leq λ\\leq λ_{0}$ and $1<γ< \\frac{n+2σ}{n-2σ}$. The two problems are known to be connected and the latter, aside from its independent interest, is actually instrumental to the former.\r\n \\smallskip\r\n At the core of our results stands a novel fractional Poincaré-type inequality expressed in terms of a new scale of $L^{2}$ fractional Sobolev spaces, which sharpens those known so far, and which holds more generally on Riemannian symmetric spaces of non-compact type. We also establish an associated Rellich--Kondrachov-like compact embedding theorem for radial functions, along with other related properties.","lang":"eng"}],"project":[{"name":"TRR 358: Ganzzahlige Strukturen in Geometrie und Darstellungstheorie","_id":"357"}],"external_id":{"arxiv":["2509.12349"]},"date_created":"2026-02-19T11:42:22Z","type":"preprint","year":"2025","status":"public","title":"Blow-up exponents and a semilinear elliptic equation for the fractional Laplacian on hyperbolic spaces","author":[{"full_name":"Bruno, Tommaso","last_name":"Bruno","first_name":"Tommaso"},{"first_name":"Efthymia","last_name":"Papageorgiou","full_name":"Papageorgiou, Efthymia","id":"100325"}],"date_updated":"2026-07-03T12:31:02Z","_id":"64267","language":[{"iso":"eng"}],"user_id":"100325"},{"date_created":"2026-01-06T09:33:28Z","type":"journal_article","issue":"4","publication":"Annali di Matematica Pura ed Applicata (1923 -)","abstract":[{"lang":"eng","text":"Abstract\r\n We prove various estimates for the asymptotics of counting functions associated to point sets of coherent frames and Riesz sequences. The obtained results recover the necessary density conditions for coherent frames and Riesz sequences for general unimodular amenable groups, while providing more precise estimates under additional localization conditions on the coherent system for groups of polynomial growth. \r\n"}],"language":[{"iso":"eng"}],"doi":"10.1007/s10231-024-01535-y","publication_identifier":{"issn":["0373-3114","1618-1891"]},"author":[{"id":"100325","full_name":"Papageorgiou, Efthymia","last_name":"Papageorgiou","first_name":"Efthymia"},{"full_name":"van Velthoven, Jordy Timo","last_name":"van Velthoven","first_name":"Jordy Timo"}],"title":"Counting function estimates for coherent frames and Riesz sequences","year":"2024","intvolume":" 204","date_updated":"2026-07-03T12:37:20Z","publication_status":"published","citation":{"short":"E. Papageorgiou, J.T. van Velthoven, Annali Di Matematica Pura Ed Applicata (1923 -) 204 (2024) 1469–1491.","chicago":"Papageorgiou, Efthymia, and Jordy Timo van Velthoven. “Counting Function Estimates for Coherent Frames and Riesz Sequences.” Annali Di Matematica Pura Ed Applicata (1923 -) 204, no. 4 (2024): 1469–91. https://doi.org/10.1007/s10231-024-01535-y.","ieee":"E. Papageorgiou and J. T. van Velthoven, “Counting function estimates for coherent frames and Riesz sequences,” Annali di Matematica Pura ed Applicata (1923 -), vol. 204, no. 4, pp. 1469–1491, 2024, doi: 10.1007/s10231-024-01535-y.","apa":"Papageorgiou, E., & van Velthoven, J. T. (2024). Counting function estimates for coherent frames and Riesz sequences. Annali Di Matematica Pura Ed Applicata (1923 -), 204(4), 1469–1491. https://doi.org/10.1007/s10231-024-01535-y","bibtex":"@article{Papageorgiou_van Velthoven_2024, title={Counting function estimates for coherent frames and Riesz sequences}, volume={204}, DOI={10.1007/s10231-024-01535-y}, number={4}, journal={Annali di Matematica Pura ed Applicata (1923 -)}, publisher={Springer Science and Business Media LLC}, author={Papageorgiou, Efthymia and van Velthoven, Jordy Timo}, year={2024}, pages={1469–1491} }","ama":"Papageorgiou E, van Velthoven JT. Counting function estimates for coherent frames and Riesz sequences. Annali di Matematica Pura ed Applicata (1923 -). 2024;204(4):1469-1491. doi:10.1007/s10231-024-01535-y","mla":"Papageorgiou, Efthymia, and Jordy Timo van Velthoven. “Counting Function Estimates for Coherent Frames and Riesz Sequences.” Annali Di Matematica Pura Ed Applicata (1923 -), vol. 204, no. 4, Springer Science and Business Media LLC, 2024, pp. 1469–91, doi:10.1007/s10231-024-01535-y."},"_id":"63500","publisher":"Springer Science and Business Media LLC","page":"1469-1491","volume":204,"user_id":"100325","status":"public"},{"_id":"53542","publisher":"Springer Science and Business Media LLC","volume":24,"user_id":"100325","status":"public","citation":{"short":"E. Papageorgiou, Journal of Evolution Equations 24 (2024).","chicago":"Papageorgiou, Efthymia. “Asymptotic Behavior of Solutions to the Extension Problem for the Fractional Laplacian on Noncompact Symmetric Spaces.” Journal of Evolution Equations 24, no. 2 (2024). https://doi.org/10.1007/s00028-024-00959-6.","apa":"Papageorgiou, E. (2024). Asymptotic behavior of solutions to the extension problem for the fractional Laplacian on noncompact symmetric spaces. Journal of Evolution Equations, 24(2), Article 34. https://doi.org/10.1007/s00028-024-00959-6","ieee":"E. Papageorgiou, “Asymptotic behavior of solutions to the extension problem for the fractional Laplacian on noncompact symmetric spaces,” Journal of Evolution Equations, vol. 24, no. 2, Art. no. 34, 2024, doi: 10.1007/s00028-024-00959-6.","ama":"Papageorgiou E. Asymptotic behavior of solutions to the extension problem for the fractional Laplacian on noncompact symmetric spaces. Journal of Evolution Equations. 2024;24(2). doi:10.1007/s00028-024-00959-6","bibtex":"@article{Papageorgiou_2024, title={Asymptotic behavior of solutions to the extension problem for the fractional Laplacian on noncompact symmetric spaces}, volume={24}, DOI={10.1007/s00028-024-00959-6}, number={234}, journal={Journal of Evolution Equations}, publisher={Springer Science and Business Media LLC}, author={Papageorgiou, Efthymia}, year={2024} }","mla":"Papageorgiou, Efthymia. “Asymptotic Behavior of Solutions to the Extension Problem for the Fractional Laplacian on Noncompact Symmetric Spaces.” Journal of Evolution Equations, vol. 24, no. 2, 34, Springer Science and Business Media LLC, 2024, doi:10.1007/s00028-024-00959-6."},"language":[{"iso":"eng"}],"article_number":"34","doi":"10.1007/s00028-024-00959-6","author":[{"id":"100325","first_name":"Efthymia","last_name":"Papageorgiou","full_name":"Papageorgiou, Efthymia"}],"publication_identifier":{"issn":["1424-3199","1424-3202"]},"title":"Asymptotic behavior of solutions to the extension problem for the fractional Laplacian on noncompact symmetric spaces","year":"2024","intvolume":" 24","date_updated":"2026-07-03T12:35:54Z","publication_status":"published","date_created":"2024-04-17T13:18:30Z","department":[{"_id":"555"}],"type":"journal_article","keyword":["Mathematics (miscellaneous)"],"publication":"Journal of Evolution Equations","issue":"2","abstract":[{"lang":"eng","text":"AbstractThis work deals with the extension problem for the fractional Laplacian on Riemannian symmetric spaces G/K of noncompact type and of general rank, which gives rise to a family of convolution operators, including the Poisson operator. More precisely, motivated by Euclidean results for the Poisson semigroup, we study the long-time asymptotic behavior of solutions to the extension problem for $$L^1$$\r\n \r\n L\r\n 1\r\n \r\n initial data. In the case of the Laplace–Beltrami operator, we show that if the initial data are bi-K-invariant, then the solution to the extension problem behaves asymptotically as the mass times the fundamental solution, but this convergence may break down in the non-bi-K-invariant case. In the second part, we investigate the long-time asymptotic behavior of the extension problem associated with the so-called distinguished Laplacian on G/K. In this case, we observe phenomena which are similar to the Euclidean setting for the Poisson semigroup, such as $$L^1$$\r\n \r\n L\r\n 1\r\n \r\n asymptotic convergence without the assumption of bi-K-invariance."}]},{"language":[{"iso":"eng"}],"article_number":"7","doi":"10.1007/s12220-024-01837-w","author":[{"id":"100325","full_name":"Papageorgiou, Efthymia","first_name":"Efthymia","last_name":"Papageorgiou"}],"publication_identifier":{"issn":["1050-6926","1559-002X"]},"year":"2024","title":"Surjectivity of Convolution Operators on Harmonic NA Groups","intvolume":" 35","date_updated":"2026-07-03T12:35:33Z","publication_status":"published","date_created":"2026-01-06T09:39:35Z","type":"journal_article","issue":"1","publication":"The Journal of Geometric Analysis","abstract":[{"lang":"eng","text":"Abstract\r\n Let \r\n \r\n $$\\mu $$\r\n \r\n μ\r\n \r\n \r\n be a radial compactly supported distribution on a harmonic NA group. We prove that the right convolution operator \r\n \r\n $$c_{\\mu }:f \\mapsto f* \\mu $$\r\n \r\n \r\n \r\n c\r\n μ\r\n \r\n :\r\n f\r\n ↦\r\n f\r\n \r\n ∗\r\n μ\r\n \r\n \r\n \r\n maps the space of smooth \r\n \r\n $$\\mathfrak {v}$$\r\n \r\n v\r\n \r\n \r\n -radial functions onto itself if and only if the spherical Fourier transform \r\n \r\n $$\\widetilde{\\mu }(\\lambda )$$\r\n \r\n \r\n \r\n μ\r\n ~\r\n \r\n \r\n (\r\n λ\r\n )\r\n \r\n \r\n \r\n \r\n , \r\n \r\n $$\\lambda \\in \\mathbb {C}$$\r\n \r\n \r\n λ\r\n ∈\r\n C\r\n \r\n \r\n \r\n , is slowly decreasing. As an application, we prove that certain averages over spheres are surjective on the space of smooth \r\n \r\n $$\\mathfrak {v}$$\r\n \r\n v\r\n \r\n \r\n -radial functions."}],"_id":"63502","publisher":"Springer Science and Business Media LLC","volume":35,"user_id":"100325","status":"public","citation":{"mla":"Papageorgiou, Efthymia. “Surjectivity of Convolution Operators on Harmonic NA Groups.” The Journal of Geometric Analysis, vol. 35, no. 1, 7, Springer Science and Business Media LLC, 2024, doi:10.1007/s12220-024-01837-w.","ama":"Papageorgiou E. Surjectivity of Convolution Operators on Harmonic NA Groups. The Journal of Geometric Analysis. 2024;35(1). doi:10.1007/s12220-024-01837-w","bibtex":"@article{Papageorgiou_2024, title={Surjectivity of Convolution Operators on Harmonic NA Groups}, volume={35}, DOI={10.1007/s12220-024-01837-w}, number={17}, journal={The Journal of Geometric Analysis}, publisher={Springer Science and Business Media LLC}, author={Papageorgiou, Efthymia}, year={2024} }","apa":"Papageorgiou, E. (2024). Surjectivity of Convolution Operators on Harmonic NA Groups. The Journal of Geometric Analysis, 35(1), Article 7. https://doi.org/10.1007/s12220-024-01837-w","ieee":"E. Papageorgiou, “Surjectivity of Convolution Operators on Harmonic NA Groups,” The Journal of Geometric Analysis, vol. 35, no. 1, Art. no. 7, 2024, doi: 10.1007/s12220-024-01837-w.","short":"E. Papageorgiou, The Journal of Geometric Analysis 35 (2024).","chicago":"Papageorgiou, Efthymia. “Surjectivity of Convolution Operators on Harmonic NA Groups.” The Journal of Geometric Analysis 35, no. 1 (2024). https://doi.org/10.1007/s12220-024-01837-w."}},{"year":"2024","title":"Large sets containing no copies of a given infinite sequence","status":"public","author":[{"full_name":"Kolountzakis, Mihail N.","last_name":"Kolountzakis","first_name":"Mihail N."},{"id":"100325","full_name":"Papageorgiou, Efthymia","last_name":"Papageorgiou","first_name":"Efthymia"}],"publication_identifier":{"issn":["1948-206X","2157-5045"]},"date_updated":"2026-07-03T12:31:35Z","publication_status":"published","intvolume":" 18","page":"93-108","language":[{"iso":"eng"}],"_id":"63504","publisher":"Mathematical Sciences Publishers","doi":"10.2140/apde.2025.18.93","user_id":"100325","volume":18,"issue":"1","publication":"Analysis & PDE","citation":{"apa":"Kolountzakis, M. N., & Papageorgiou, E. (2024). Large sets containing no copies of a given infinite sequence. Analysis & PDE, 18(1), 93–108. https://doi.org/10.2140/apde.2025.18.93","ieee":"M. N. Kolountzakis and E. Papageorgiou, “Large sets containing no copies of a given infinite sequence,” Analysis & PDE, vol. 18, no. 1, pp. 93–108, 2024, doi: 10.2140/apde.2025.18.93.","short":"M.N. Kolountzakis, E. Papageorgiou, Analysis & PDE 18 (2024) 93–108.","chicago":"Kolountzakis, Mihail N., and Efthymia Papageorgiou. “Large Sets Containing No Copies of a given Infinite Sequence.” Analysis & PDE 18, no. 1 (2024): 93–108. https://doi.org/10.2140/apde.2025.18.93.","mla":"Kolountzakis, Mihail N., and Efthymia Papageorgiou. “Large Sets Containing No Copies of a given Infinite Sequence.” Analysis & PDE, vol. 18, no. 1, Mathematical Sciences Publishers, 2024, pp. 93–108, doi:10.2140/apde.2025.18.93.","ama":"Kolountzakis MN, Papageorgiou E. Large sets containing no copies of a given infinite sequence. Analysis & PDE. 2024;18(1):93-108. doi:10.2140/apde.2025.18.93","bibtex":"@article{Kolountzakis_Papageorgiou_2024, title={Large sets containing no copies of a given infinite sequence}, volume={18}, DOI={10.2140/apde.2025.18.93}, number={1}, journal={Analysis & PDE}, publisher={Mathematical Sciences Publishers}, author={Kolountzakis, Mihail N. and Papageorgiou, Efthymia}, year={2024}, pages={93–108} }"},"date_created":"2026-01-06T09:43:35Z","type":"journal_article"},{"date_updated":"2024-04-17T13:14:23Z","publication_status":"published","title":"Asymptotic Behavior of the Heat Semigroup on Certain Riemannian Manifolds","year":"2023","status":"public","author":[{"first_name":"Alexander","last_name":"Grigor'yan","full_name":"Grigor'yan, Alexander"},{"id":"100325","full_name":"Papageorgiou, Efthymia","first_name":"Efthymia","last_name":"Papageorgiou"},{"full_name":"Zhang, Hong-Wei","first_name":"Hong-Wei","last_name":"Zhang"}],"publication_identifier":{"isbn":["9783031377990","9783031378003"],"issn":["2296-5009","2296-5017"]},"doi":"10.1007/978-3-031-37800-3","user_id":"100325","editor":[{"full_name":"Alonso Ruiz, Patricia","last_name":"Alonso Ruiz","first_name":"Patricia"},{"last_name":"Hinz","first_name":"Michael","full_name":"Hinz, Michael"},{"last_name":"Okoudjou","first_name":"Kasso A.","full_name":"Okoudjou, Kasso A."},{"full_name":"Rogers, Luke G.","last_name":"Rogers","first_name":"Luke G."},{"full_name":"Teplyaev, Alexander","first_name":"Alexander","last_name":"Teplyaev"}],"_id":"53537","publisher":"Springer International Publishing","language":[{"iso":"eng"}],"publication":"From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1","citation":{"mla":"Grigor’yan, Alexander, et al. “Asymptotic Behavior of the Heat Semigroup on Certain Riemannian Manifolds.” From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1, edited by Patricia Alonso Ruiz et al., Springer International Publishing, 2023, doi:10.1007/978-3-031-37800-3.","apa":"Grigor’yan, A., Papageorgiou, E., & Zhang, H.-W. (2023). Asymptotic Behavior of the Heat Semigroup on Certain Riemannian Manifolds. In P. Alonso Ruiz, M. Hinz, K. A. Okoudjou, L. G. Rogers, & A. Teplyaev (Eds.), From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1. Springer International Publishing. https://doi.org/10.1007/978-3-031-37800-3","ieee":"A. Grigor’yan, E. Papageorgiou, and H.-W. Zhang, “Asymptotic Behavior of the Heat Semigroup on Certain Riemannian Manifolds,” in From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1, P. Alonso Ruiz, M. Hinz, K. A. Okoudjou, L. G. Rogers, and A. Teplyaev, Eds. Cham: Springer International Publishing, 2023.","short":"A. Grigor’yan, E. Papageorgiou, H.-W. Zhang, in: P. Alonso Ruiz, M. Hinz, K.A. Okoudjou, L.G. Rogers, A. Teplyaev (Eds.), From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1, Springer International Publishing, Cham, 2023.","ama":"Grigor’yan A, Papageorgiou E, Zhang H-W. Asymptotic Behavior of the Heat Semigroup on Certain Riemannian Manifolds. In: Alonso Ruiz P, Hinz M, Okoudjou KA, Rogers LG, Teplyaev A, eds. From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1. Springer International Publishing; 2023. doi:10.1007/978-3-031-37800-3","chicago":"Grigor’yan, Alexander, Efthymia Papageorgiou, and Hong-Wei Zhang. “Asymptotic Behavior of the Heat Semigroup on Certain Riemannian Manifolds.” In From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1, edited by Patricia Alonso Ruiz, Michael Hinz, Kasso A. Okoudjou, Luke G. Rogers, and Alexander Teplyaev. Cham: Springer International Publishing, 2023. https://doi.org/10.1007/978-3-031-37800-3.","bibtex":"@inbook{Grigor’yan_Papageorgiou_Zhang_2023, place={Cham}, title={Asymptotic Behavior of the Heat Semigroup on Certain Riemannian Manifolds}, DOI={10.1007/978-3-031-37800-3}, booktitle={From Classical Analysis to Analysis on Fractals. A Tribute to Robert Strichartz, Volume 1}, publisher={Springer International Publishing}, author={Grigor’yan, Alexander and Papageorgiou, Efthymia and Zhang, Hong-Wei}, editor={Alonso Ruiz, Patricia and Hinz, Michael and Okoudjou, Kasso A. and Rogers, Luke G. and Teplyaev, Alexander}, year={2023} }"},"type":"book_chapter","place":"Cham","date_created":"2024-04-17T13:11:15Z"},{"abstract":[{"text":"AbstractWe study harmonic maps from a subset of the complex plane to a subset of the hyperbolic plane. In Fotiadis and Daskaloyannis (Nonlinear Anal 214, 112546, 2022), harmonic maps are related to the sinh-Gordon equation and a Bäcklund transformation is introduced, which connects solutions of the sinh-Gordon and sine-Gordon equation. We develop this machinery in order to construct new harmonic maps to the hyperbolic plane.","lang":"eng"}],"publication":"Revista Matemática Complutense","citation":{"apa":"Polychrou, G., Papageorgiou, E., Fotiadis, A., & Daskaloyannis, C. (2023). New examples of harmonic maps to the hyperbolic plane via Bäcklund transformation. Revista Matemática Complutense. https://doi.org/10.1007/s13163-023-00476-z","ieee":"G. Polychrou, E. Papageorgiou, A. Fotiadis, and C. Daskaloyannis, “New examples of harmonic maps to the hyperbolic plane via Bäcklund transformation,” Revista Matemática Complutense, 2023, doi: 10.1007/s13163-023-00476-z.","chicago":"Polychrou, G., Efthymia Papageorgiou, A. Fotiadis, and C. Daskaloyannis. “New Examples of Harmonic Maps to the Hyperbolic Plane via Bäcklund Transformation.” Revista Matemática Complutense, 2023. https://doi.org/10.1007/s13163-023-00476-z.","short":"G. Polychrou, E. Papageorgiou, A. Fotiadis, C. Daskaloyannis, Revista Matemática Complutense (2023).","mla":"Polychrou, G., et al. “New Examples of Harmonic Maps to the Hyperbolic Plane via Bäcklund Transformation.” Revista Matemática Complutense, Springer Science and Business Media LLC, 2023, doi:10.1007/s13163-023-00476-z.","ama":"Polychrou G, Papageorgiou E, Fotiadis A, Daskaloyannis C. New examples of harmonic maps to the hyperbolic plane via Bäcklund transformation. Revista Matemática Complutense. Published online 2023. doi:10.1007/s13163-023-00476-z","bibtex":"@article{Polychrou_Papageorgiou_Fotiadis_Daskaloyannis_2023, title={New examples of harmonic maps to the hyperbolic plane via Bäcklund transformation}, DOI={10.1007/s13163-023-00476-z}, journal={Revista Matemática Complutense}, publisher={Springer Science and Business Media LLC}, author={Polychrou, G. and Papageorgiou, Efthymia and Fotiadis, A. and Daskaloyannis, C.}, year={2023} }"},"keyword":["General Mathematics"],"type":"journal_article","department":[{"_id":"555"}],"date_created":"2024-04-17T13:15:07Z","date_updated":"2024-04-17T13:15:51Z","publication_status":"published","year":"2023","status":"public","title":"New examples of harmonic maps to the hyperbolic plane via Bäcklund transformation","author":[{"full_name":"Polychrou, G.","first_name":"G.","last_name":"Polychrou"},{"id":"100325","full_name":"Papageorgiou, Efthymia","last_name":"Papageorgiou","first_name":"Efthymia"},{"full_name":"Fotiadis, A.","last_name":"Fotiadis","first_name":"A."},{"last_name":"Daskaloyannis","first_name":"C.","full_name":"Daskaloyannis, C."}],"publication_identifier":{"issn":["1139-1138","1988-2807"]},"doi":"10.1007/s13163-023-00476-z","user_id":"100325","publisher":"Springer Science and Business Media LLC","_id":"53538","language":[{"iso":"eng"}]},{"author":[{"last_name":"Papageorgiou","first_name":"Efthymia","full_name":"Papageorgiou, Efthymia","id":"100325"}],"publication_identifier":{"issn":["0926-2601","1572-929X"]},"title":"Large-Time Behavior of Two Families of Operators Related to the Fractional Laplacian on Certain Riemannian Manifolds","year":"2023","status":"public","publication_status":"published","date_updated":"2026-07-03T12:37:31Z","publisher":"Springer Science and Business Media LLC","_id":"53540","language":[{"iso":"eng"}],"user_id":"100325","doi":"10.1007/s11118-023-10109-1","citation":{"short":"E. Papageorgiou, Potential Analysis (2023).","chicago":"Papageorgiou, Efthymia. “Large-Time Behavior of Two Families of Operators Related to the Fractional Laplacian on Certain Riemannian Manifolds.” Potential Analysis, 2023. https://doi.org/10.1007/s11118-023-10109-1.","ieee":"E. Papageorgiou, “Large-Time Behavior of Two Families of Operators Related to the Fractional Laplacian on Certain Riemannian Manifolds,” Potential Analysis, 2023, doi: 10.1007/s11118-023-10109-1.","apa":"Papageorgiou, E. (2023). Large-Time Behavior of Two Families of Operators Related to the Fractional Laplacian on Certain Riemannian Manifolds. Potential Analysis. https://doi.org/10.1007/s11118-023-10109-1","bibtex":"@article{Papageorgiou_2023, title={Large-Time Behavior of Two Families of Operators Related to the Fractional Laplacian on Certain Riemannian Manifolds}, DOI={10.1007/s11118-023-10109-1}, journal={Potential Analysis}, publisher={Springer Science and Business Media LLC}, author={Papageorgiou, Efthymia}, year={2023} }","ama":"Papageorgiou E. Large-Time Behavior of Two Families of Operators Related to the Fractional Laplacian on Certain Riemannian Manifolds. Potential Analysis. Published online 2023. doi:10.1007/s11118-023-10109-1","mla":"Papageorgiou, Efthymia. “Large-Time Behavior of Two Families of Operators Related to the Fractional Laplacian on Certain Riemannian Manifolds.” Potential Analysis, Springer Science and Business Media LLC, 2023, doi:10.1007/s11118-023-10109-1."},"publication":"Potential Analysis","abstract":[{"lang":"eng","text":"AbstractThis note is concerned with two families of operators related to the fractional Laplacian, the first arising from the Caffarelli-Silvestre extension problem and the second from the fractional heat equation. They both include the Poisson semigroup. We show that on a complete, connected, and non-compact Riemannian manifold of non-negative Ricci curvature, in both cases, the solution with $$L^1$$\r\n \r\n L\r\n 1\r\n \r\n initial data behaves asymptotically as the mass times the fundamental solution. Similar long-time convergence results remain valid on more general manifolds satisfying the Li-Yau two-sided estimate of the heat kernel. The situation changes drastically on hyperbolic space, and more generally on rank one non-compact symmetric spaces: we show that for the Poisson semigroup, the convergence to the Poisson kernel fails -but remains true under the additional assumption of radial initial data."}],"date_created":"2024-04-17T13:17:37Z","department":[{"_id":"555"}],"type":"journal_article","keyword":["Analysis"]},{"_id":"53539","language":[{"iso":"eng"}],"publisher":"Springer Science and Business Media LLC","user_id":"100325","doi":"10.1007/s41808-023-00250-8","status":"public","title":"Asymptotics for the infinite Brownian loop on noncompact symmetric spaces","year":"2023","author":[{"id":"100325","full_name":"Papageorgiou, Efthymia","first_name":"Efthymia","last_name":"Papageorgiou"}],"publication_identifier":{"issn":["2296-9020","2296-9039"]},"publication_status":"published","date_updated":"2026-07-03T12:36:17Z","date_created":"2024-04-17T13:16:39Z","type":"journal_article","keyword":["Applied Mathematics","Numerical Analysis","Analysis"],"department":[{"_id":"555"}],"publication":"Journal of Elliptic and Parabolic Equations","citation":{"apa":"Papageorgiou, E. (2023). Asymptotics for the infinite Brownian loop on noncompact symmetric spaces. Journal of Elliptic and Parabolic Equations. https://doi.org/10.1007/s41808-023-00250-8","ieee":"E. Papageorgiou, “Asymptotics for the infinite Brownian loop on noncompact symmetric spaces,” Journal of Elliptic and Parabolic Equations, 2023, doi: 10.1007/s41808-023-00250-8.","chicago":"Papageorgiou, Efthymia. “Asymptotics for the Infinite Brownian Loop on Noncompact Symmetric Spaces.” Journal of Elliptic and Parabolic Equations, 2023. https://doi.org/10.1007/s41808-023-00250-8.","short":"E. Papageorgiou, Journal of Elliptic and Parabolic Equations (2023).","mla":"Papageorgiou, Efthymia. “Asymptotics for the Infinite Brownian Loop on Noncompact Symmetric Spaces.” Journal of Elliptic and Parabolic Equations, Springer Science and Business Media LLC, 2023, doi:10.1007/s41808-023-00250-8.","ama":"Papageorgiou E. Asymptotics for the infinite Brownian loop on noncompact symmetric spaces. Journal of Elliptic and Parabolic Equations. Published online 2023. doi:10.1007/s41808-023-00250-8","bibtex":"@article{Papageorgiou_2023, title={Asymptotics for the infinite Brownian loop on noncompact symmetric spaces}, DOI={10.1007/s41808-023-00250-8}, journal={Journal of Elliptic and Parabolic Equations}, publisher={Springer Science and Business Media LLC}, author={Papageorgiou, Efthymia}, year={2023} }"},"abstract":[{"lang":"eng","text":"AbstractThe infinite Brownian loop on a Riemannian manifold is the limit in distribution of the Brownian bridge of length T around a fixed origin when $$T \\rightarrow +\\infty $$\r\n \r\n T\r\n →\r\n +\r\n ∞\r\n \r\n . The aim of this note is to study its long-time asymptotics on Riemannian symmetric spaces G/K of noncompact type and of general rank. This amounts to the behavior of solutions to the heat equation subject to the Doob transform induced by the ground spherical function. Unlike the standard Brownian motion, we observe in this case phenomena which are similar to the Euclidean setting, namely $$L^1$$\r\n \r\n L\r\n 1\r\n \r\n asymptotic convergence without requiring bi-K-invariance for initial data, and strong $$L^{\\infty }$$\r\n \r\n L\r\n ∞\r\n \r\n convergence."}]}]