Anastasios Sidiropoulos

131 papers A* 32A 4B 5C 2Journal 69Unranked 18

Year	Rank	Type	Title / Venue / Authors
2025	J	`jnl`	Geometric Algorithms for k-NN Poisoning. Comput. Geom. Topol. Diego Ihara Centurion, Karine Chubarian, Bohan Fan, Francesco Sgherzi, Thiruvenkadam S. Radhakrishnan, Anastasios Sidiropoulos, Angelo Straight
2024	C	`conf`	Rational Economic Behaviours in the Bitcoin Lightning Network. ICBC Andrea Carotti, Cosimo Sguanci, Anastasios Sidiropoulos
2023	—	`conf`	Geometric Algorithms for k-NN Poisoning. CCCG Diego Ihara, Karine Chubarian, Bohan Fan, Francesco Sgherzi, Thiruvenkadam S. Radhakrishnan, Anastasios Sidiropoulos, Angelo Straight
2023	J	`jnl`	Geometric Algorithms for k-NN Poisoning. CoRR Diego Ihara Centurion, Karine Chubarian, Bohan Fan, Francesco Sgherzi, Thiruvenkadam S. Radhakrishnan, Anastasios Sidiropoulos, Angelo Straight
2023	C	`conf`	Mass Exit Attacks on the Lightning Network. ICBC Cosimo Sguanci, Anastasios Sidiropoulos
2023	J	`jnl`	Maximizing Coverage While Ensuring Fairness: A Tale of Conflicting Objectives. Algorithmica Abolfazl Asudeh, Tanya Y. Berger-Wolf, Bhaskar DasGupta, Anastasios Sidiropoulos
2023	J	`jnl`	Rational Economic Behaviours in the Bitcoin Lightning Network. CoRR Andrea Carotti, Cosimo Sguanci, Anastasios Sidiropoulos
2022	J	`jnl`	Mass Exit Attacks on the Lightning Network. CoRR Cosimo Sguanci, Anastasios Sidiropoulos
2021	A*	`conf`	Embeddings of Planar Quasimetrics into Directed ℓ1 and Polylogarithmic Approximation for Directed Sparsest-Cut. FOCS Ken-ichi Kawarabayashi, Anastasios Sidiropoulos
2021	J	`jnl`	Embeddings of Planar Quasimetrics into Directed 𝓁 CoRR Ken-ichi Kawarabayashi, Anastasios Sidiropoulos
2021	J	`jnl`	Fractal Dimension and Lower Bounds for Geometric Problems. Discret. Comput. Geom. Anastasios Sidiropoulos, Kritika Singhal, Vijay Sridhar
2021	—	`conf`	Grouping Words with Semantic Diversity. NAACL-HLT Karine Chubarian, Abdul Rafae Khan, Anastasios Sidiropoulos, Jia Xu
2021	A*	`conf`	NN-Baker: A Neural-network Infused Algorithmic Framework for Optimization Problems on Geometric Intersection Graphs. NeurIPS Evan McCarty, Qi Zhao, Anastasios Sidiropoulos, Yusu Wang
2020	J	`jnl`	Approximate greedy clustering and distance selection for graph metrics. J. Comput. Geom. David Eppstein, Sariel Har-Peled, Anastasios Sidiropoulos
2020	—	`conf`	Computing Bi-Lipschitz Outlier Embeddings into the Line. APPROX-RANDOM Karine Chubarian, Anastasios Sidiropoulos
2020	J	`jnl`	Computing Bi-Lipschitz Outlier Embeddings into the Line. CoRR Karine Chubarian, Anastasios Sidiropoulos
2020	—	`conf`	Learning Lines with Ordinal Constraints. APPROX-RANDOM Bohan Fan, Diego Ihara, Neshat Mohammadi, Francesco Sgherzi, Anastasios Sidiropoulos, Mina Valizadeh
2020	J	`jnl`	Learning Lines with Ordinal Constraints. CoRR Diego Ihara Centurion, Bohan Fan, Francesco Sgherzi, Anastasios Sidiropoulos
2020	J	`jnl`	Maximizing coverage while ensuring fairness: a tale of conflicting objective. CoRR Abolfazl Asudeh, Tanya Y. Berger-Wolf, Bhaskar DasGupta, Anastasios Sidiropoulos
2020	J	`jnl`	On theoretical and empirical algorithmic analysis of the efficiency gap measure in partisan gerrymandering. J. Comb. Optim. Tanima Chatterjee, Bhaskar DasGupta, Laura Palmieri, Zainab Al-Qurashi, Anastasios Sidiropoulos
2020	A	`conf`	Topology-aware Parallel Data Processing: Models, Algorithms and Systems at Scale. CIDR Spyros Blanas, Paraschos Koutris, Anastasios Sidiropoulos
2019	A*	`conf`	A Polynomial Time Algorithm for Log-Concave Maximum Likelihood via Locally Exponential Families. NeurIPS Brian Axelrod, Ilias Diakonikolas, Alistair Stewart, Anastasios Sidiropoulos, Gregory Valiant
2019	J	`jnl`	A Polynomial Time Algorithm for Log-Concave Maximum Likelihood via Locally Exponential Families. CoRR Brian Axelrod, Ilias Diakonikolas, Anastasios Sidiropoulos, Alistair Stewart, Gregory Valiant
2019	A*	`conf`	Algorithms for Metric Learning via Contrastive Embeddings. SoCG Diego Ihara, Neshat Mohammadi, Anastasios Sidiropoulos
2019	J	`jnl`	Approximation Algorithms for Low-Distortion Embeddings into Low-Dimensional Spaces. SIAM J. Discret. Math. Anastasios Sidiropoulos, Mihai Badoiu, Kedar Dhamdhere, Anupam Gupta, Piotr Indyk, Yuri Rabinovich, Harald Räcke, R. Ravi
2019	—	`conf`	Brain Dynamics Through the Lens of Statistical Mechanics by Unifying Structure and Function. MICCAI (5) Igor Fortel, Mitchell Butler, Laura E. Korthauer, Liang Zhan, Olusola Ajilore, Ira Driscoll, Anastasios Sidiropoulos, Yanfu Zhang, Lei Guo, Heng Huang, Dan Schonfeld, Alex D. Leow
2019	J	`jnl`	Learning Mahalanobis Metric Spaces via Geometric Approximation Algorithms. CoRR Diego Ihara, Neshat Mohammadi, Anastasios Sidiropoulos
2019	A*	`conf`	On Constant Multi-Commodity Flow-Cut Gaps for Families of Directed Minor-Free Graphs. SODA Ario Salmasi, Anastasios Sidiropoulos, Vijay Sridhar
2019	A*	`conf`	Polylogarithmic approximation for Euler genus on bounded degree graphs. STOC Ken-ichi Kawarabayashi, Anastasios Sidiropoulos
2019	—	`conf`	Routing Symmetric Demands in Directed Minor-Free Graphs with Constant Congestion. APPROX-RANDOM Timothy Carpenter, Ario Salmasi, Anastasios Sidiropoulos
2019	J	`jnl`	Spectral concentration and greedy Comput. Geom. Tamal K. Dey, Pan Peng, Alfred Rossi, Anastasios Sidiropoulos
2018	J	`jnl`	A Polynomial Time Algorithm for Maximum Likelihood Estimation of Multivariate Log-concave Densities. CoRR Ilias Diakonikolas, Anastasios Sidiropoulos, Alistair Stewart
2018	A*	`conf`	Algorithms for Low-Distortion Embeddings into Arbitrary 1-Dimensional Spaces. SoCG Timothy Carpenter, Fedor V. Fomin, Daniel Lokshtanov, Saket Saurabh, Anastasios Sidiropoulos
2018	J	`jnl`	Algorithms for metric learning via contrastive embeddings. CoRR Diego Ihara Centurion, Neshat Mohammadi, Anastasios Sidiropoulos
2018	J	`jnl`	Alleviating partisan gerrymandering: can math and computers help to eliminate wasted votes? CoRR Tanima Chatterjee, Bhaskar DasGupta, Laura Palmieri, Zainab Al-Qurashi, Anastasios Sidiropoulos
2018	J	`jnl`	Approximation Algorithms for Euler Genus and Related Problems. SIAM J. Comput. Chandra Chekuri, Anastasios Sidiropoulos
2018	J	`jnl`	Chasing Similarity: Distribution-aware Aggregation Scheduling (Extended Version). CoRR Feilong Liu, Ario Salmasi, Spyros Blanas, Anastasios Sidiropoulos
2018	J	`jnl`	Chasing Similarity: Distribution-aware Aggregation Scheduling. Proc. VLDB Endow. Feilong Liu, Ario Salmasi, Spyros Blanas, Anastasios Sidiropoulos
2018	J	`jnl`	Computing the Gromov-Hausdorff Distance for Metric Trees. ACM Trans. Algorithms Pankaj K. Agarwal, Kyle Fox, Abhinandan Nath, Anastasios Sidiropoulos, Yusu Wang
2018	A*	`conf`	Fractal Dimension and Lower Bounds for Geometric Problems. SoCG Anastasios Sidiropoulos, Kritika Singhal, Vijay Sridhar
2018	A*	`conf`	Near-Optimal Sample Complexity Bounds for Maximum Likelihood Estimation of Multivariate Log-concave Densities. COLT Timothy Carpenter, Ilias Diakonikolas, Anastasios Sidiropoulos, Alistair Stewart
2018	J	`jnl`	Near-Optimal Sample Complexity Bounds for Maximum Likelihood Estimation of Multivariate Log-concave Densities. CoRR Timothy Carpenter, Ilias Diakonikolas, Anastasios Sidiropoulos, Alistair Stewart
2018	J	`jnl`	Quasimetric Embeddings and Their Applications. Algorithmica Facundo Mémoli, Anastasios Sidiropoulos, Vijay Sridhar
2018	J	`jnl`	Sketching and Clustering Metric Measure Spaces. CoRR Facundo Mémoli, Anastasios Sidiropoulos, Kritika Singhal
2017	J	`jnl`	A Pseudo-Approximation for the Genus of Hamiltonian Graphs. Theory Comput. Yury Makarychev, Amir Nayyeri, Anastasios Sidiropoulos
2017	A*	`conf`	Algorithmic Interpretations of Fractal Dimension. SoCG Anastasios Sidiropoulos, Vijay Sridhar
2017	J	`jnl`	Algorithmic interpretations of fractal dimension. CoRR Anastasios Sidiropoulos, Vijay Sridhar
2017	J	`jnl`	Algorithms for low-distortion embeddings into arbitrary 1-dimensional spaces. CoRR Timothy Carpenter, Fedor V. Fomin, Daniel Lokshtanov, Saket Saurabh, Anastasios Sidiropoulos
2017	J	`jnl`	Fractal dimension and lower bounds for geometric problems. CoRR Anastasios Sidiropoulos, Kritika Singhal, Vijay Sridhar
2017	A*	`conf`	Metric embeddings with outliers. SODA Anastasios Sidiropoulos, Dingkang Wang, Yusu Wang
2017	J	`jnl`	On constant multi-commodity flow-cut gaps for directed minor-free graphs. CoRR Ario Salmasi, Anastasios Sidiropoulos, Vijay Sridhar
2017	A*	`conf`	Polylogarithmic Approximation for Minimum Planarization (Almost). FOCS Ken-ichi Kawarabayashi, Anastasios Sidiropoulos
2017	J	`jnl`	Polylogarithmic approximation for minimum planarization (almost). CoRR Ken-ichi Kawarabayashi, Anastasios Sidiropoulos
2017	J	`jnl`	Routing Symmetric Demands in Directed Minor-Free Graphs with Constant Congestion. CoRR Timothy Carpenter, Ario Salmasi, Anastasios Sidiropoulos
2017	A	`conf`	Temporal Clustering. ESA Tamal K. Dey, Alfred Rossi, Anastasios Sidiropoulos
2017	J	`jnl`	Temporal Clustering. CoRR Tamal K. Dey, Alfred Rossi, Anastasios Sidiropoulos
2017	B	`conf`	Temporal Hierarchical Clustering. ISAAC Tamal K. Dey, Alfred Rossi, Anastasios Sidiropoulos
2017	J	`jnl`	Temporal Hierarchical Clustering. CoRR Tamal K. Dey, Alfred Rossi, Anastasios Sidiropoulos
2016	B	`conf`	Brief Announcement: Approximating the I/O Complexity of One-Shot Red-Blue Pebbling. SPAA Timothy Carpenter, Fabrice Rastello, P. Sadayappan, Anastasios Sidiropoulos
2016	—	`conf`	Constant-Distortion Embeddings of Hausdorff Metrics into Constant-Dimensional l_p Spaces. APPROX-RANDOM Arturs Backurs, Anastasios Sidiropoulos
2016	—	`conf`	Constant-Factor Approximations for Asymmetric TSP on Nearly-Embeddable Graphs. APPROX-RANDOM Dániel Marx, Ario Salmasi, Anastasios Sidiropoulos
2016	J	`jnl`	Constant-factor approximations for asymmetric TSP on nearly-embeddable graphs. CoRR Dániel Marx, Ario Salmasi, Anastasios Sidiropoulos
2016	J	`jnl`	How to Walk Your Dog in the Mountains with No Magic Leash. Discret. Comput. Geom. Sariel Har-Peled, Amir Nayyeri, Mohammad R. Salavatipour, Anastasios Sidiropoulos
2016	J	`jnl`	Layouts of Expander Graphs. Chic. J. Theor. Comput. Sci. Vida Dujmovic, Anastasios Sidiropoulos, David R. Wood
2016	A*	`conf`	Quasimetric Embeddings and Their Applications. ICALP Facundo Mémoli, Anastasios Sidiropoulos, Vijay Sridhar
2016	J	`jnl`	Quasimetric embeddings and their applications. CoRR Facundo Mémoli, Anastasios Sidiropoulos, Vijay Sridhar
2016	J	`jnl`	The limited blessing of low dimensionality: when $1-1/d$ is the best possible exponent for $d$-dimensional geometric problems. CoRR Dániel Marx, Anastasios Sidiropoulos
2015	J	`jnl`	3-Monotone Expanders. CoRR Vida Dujmovic, Anastasios Sidiropoulos, David R. Wood
2015	J	`jnl`	Approximate Greedy Clustering and Distance Selection for Graph Metrics. CoRR David Eppstein, Sariel Har-Peled, Anastasios Sidiropoulos
2015	A*	`conf`	Beyond the Euler Characteristic: Approximating the Genus of General Graphs. STOC Ken-ichi Kawarabayashi, Anastasios Sidiropoulos
2015	—	`conf`	Computing the Fréchet Distance Between Polygons with Holes. ICALP (1) Amir Nayyeri, Anastasios Sidiropoulos
2015	B	`conf`	Computing the Gromov-Hausdorff Distance for Metric Trees. ISAAC Pankaj K. Agarwal, Kyle Fox, Abhinandan Nath, Anastasios Sidiropoulos, Yusu Wang
2015	J	`jnl`	Computing the Gromov-Hausdorff Distance for Metric Trees. CoRR Pankaj K. Agarwal, Kyle Fox, Abhinandan Nath, Anastasios Sidiropoulos, Yusu Wang
2015	J	`jnl`	Metric embedding with outliers. CoRR Anastasios Sidiropoulos, Yusu Wang
2014	A*	`conf`	A near-optimal approximation algorithm for Asymmetric TSP on embedded graphs. SoCG Jeff Erickson, Anastasios Sidiropoulos
2014	J	`jnl`	Beyond the Euler characteristic: Approximating the genus of general graphs. CoRR Ken-ichi Kawarabayashi, Anastasios Sidiropoulos
2014	J	`jnl`	How to Walk Your Dog in the Mountains with No Magic Leash. CoRR Sariel Har-Peled, Amir Nayyeri, Mohammad R. Salavatipour, Anastasios Sidiropoulos
2014	A*	`conf`	Minimum SODA Anupam Gupta, Anastasios Sidiropoulos
2014	J	`jnl`	Spectral concentration, robust k-center, and simple clustering. CoRR Tamal K. Dey, Alfred Rossi, Anastasios Sidiropoulos
2014	A*	`conf`	The limited blessing of low dimensionality: when 1-1/d is the best possible exponent for d-dimensional geometric problems. SoCG Dániel Marx, Anastasios Sidiropoulos
2013	—	`conf`	A Pseudo-approximation for the Genus of Hamiltonian Graphs. APPROX-RANDOM Yury Makarychev, Amir Nayyeri, Anastasios Sidiropoulos
2013	J	`jnl`	A near-optimal approximation algorithm for Asymmetric TSP on embedded graphs CoRR Jeff Erickson, Anastasios Sidiropoulos
2013	A*	`conf`	Approximation Algorithms for Euler Genus and Related Problems. FOCS Chandra Chekuri, Anastasios Sidiropoulos
2013	J	`jnl`	Approximation algorithms for Euler genus and related problems CoRR Chandra Chekuri, Anastasios Sidiropoulos
2013	A*	`conf`	Euclidean spanners in high dimensions. SODA Sariel Har-Peled, Piotr Indyk, Anastasios Sidiropoulos
2013	J	`jnl`	Fat Polygonal Partitions with Applications to Visualization and Embeddings. J. Comput. Geom. Mark de Berg, Krzysztof Onak, Anastasios Sidiropoulos
2013	J	`jnl`	Minimum d-dimensional arrangement with fixed points. CoRR Anupam Gupta, Anastasios Sidiropoulos
2013	A*	`conf`	Non-positive Curvature and the Planar Embedding Conjecture. FOCS Anastasios Sidiropoulos
2013	J	`jnl`	Non-positive curvature, and the planar embedding conjecture CoRR Anastasios Sidiropoulos
2013	J	`jnl`	Pathwidth, trees, and random embeddings. Comb. James R. Lee, Anastasios Sidiropoulos
2012	J	`jnl`	Convergence and approximation in potential games. Theor. Comput. Sci. George Christodoulou, Vahab S. Mirrokni, Anastasios Sidiropoulos
2012	—	`conf`	How to walk your dog in the mountains with no magic leash. SCG Sariel Har-Peled, Amir Nayyeri, Mohammad R. Salavatipour, Anastasios Sidiropoulos
2012	J	`jnl`	Planarizing an Unknown Surface CoRR Yury Makarychev, Anastasios Sidiropoulos
2012	—	`conf`	Planarizing an Unknown Surface. APPROX-RANDOM Yury Makarychev, Anastasios Sidiropoulos
2011	A	`conf`	Computationally Limited Randomness. ICS Matei David, Phuong Nguyen, Periklis A. Papakonstantinou, Anastasios Sidiropoulos
2011	J	`jnl`	How strong is Nisanʼs pseudo-random generator? Inf. Process. Lett. Matei David, Periklis A. Papakonstantinou, Anastasios Sidiropoulos
2011	A*	`conf`	Near-optimal distortion bounds for embedding doubling spaces into L STOC James R. Lee, Anastasios Sidiropoulos
2011	A*	`conf`	On Graph Crossing Number and Edge Planarization. SODA Julia Chuzhoy, Yury Makarychev, Anastasios Sidiropoulos
2010	J	`jnl`	Fat Polygonal Partitions with Applications to Visualization and Embeddings CoRR Mark de Berg, Krzysztof Onak, Anastasios Sidiropoulos
2010	A*	`conf`	Genus and the Geometry of the Cut Graph. SODA James R. Lee, Anastasios Sidiropoulos
2010	A*	`conf`	Inapproximability for Planar Embedding Problems. SODA Jeff Edmonds, Anastasios Sidiropoulos, Anastasios Zouzias
2010	J	`jnl`	On Graph Crossing Number and Edge Planarization CoRR Julia Chuzhoy, Yury Makarychev, Anastasios Sidiropoulos
2010	J	`jnl`	On distributing symmetric streaming computations. ACM Trans. Algorithms Jon Feldman, S. Muthukrishnan, Anastasios Sidiropoulos, Clifford Stein, Zoya Svitkina
2010	—	`conf`	Online Embeddings. APPROX-RANDOM Piotr Indyk, Avner Magen, Anastasios Sidiropoulos, Anastasios Zouzias
2010	A*	`conf`	Optimal Stochastic Planarization. FOCS Anastasios Sidiropoulos
2010	J	`jnl`	Optimal stochastic planarization CoRR Anastasios Sidiropoulos
2010	J	`jnl`	Randomly removing g handles at once CoRR Glencora Borradaile, James R. Lee, Anastasios Sidiropoulos
2010	J	`jnl`	Randomly removing g handles at once. Comput. Geom. Glencora Borradaile, James R. Lee, Anastasios Sidiropoulos
2010	J	`jnl`	Undecidability and intractability results concerning datalog programs and their persistency numbers. ACM Trans. Comput. Log. Stavros S. Cosmadakis, Eugénie Foustoucos, Anastasios Sidiropoulos
2009	A*	`conf`	On the geometry of graphs with a forbidden minor. STOC James R. Lee, Anastasios Sidiropoulos
2009	J	`jnl`	Pathwidth, trees, and random embeddings CoRR James R. Lee, Anastasios Sidiropoulos
2009	J	`jnl`	Polynomial Time with Restricted Use of Randomness. Electron. Colloquium Comput. Complex. Matei David, Periklis A. Papakonstantinou, Anastasios Sidiropoulos
2009	—	`conf`	Randomly removing g handles at once. SCG Glencora Borradaile, James R. Lee, Anastasios Sidiropoulos
2009	B	`conf`	Streaming Embeddings with Slack. WADS Christiane Lammersen, Anastasios Sidiropoulos, Christian Sohler
2008	—	`conf`	Circular partitions with applications to visualization and embeddings. SCG Krzysztof Onak, Anastasios Sidiropoulos
2008	—	`—`	Computational metric embeddings. Anastasios Sidiropoulos
2008	A*	`conf`	Inapproximability for Metric Embeddings into R^d. FOCS Jirí Matousek, Anastasios Sidiropoulos
2008	J	`jnl`	Inapproximability for metric embeddings into R^d CoRR Jirí Matousek, Anastasios Sidiropoulos
2008	A*	`conf`	On distributing symmetric streaming computations. SODA Jon Feldman, S. Muthukrishnan, Anastasios Sidiropoulos, Clifford Stein, Zoya Svitkina
2008	—	`conf`	Ordinal Embedding: Approximation Algorithms and Dimensionality Reduction. APPROX-RANDOM Mihai Badoiu, Erik D. Demaine, MohammadTaghi Hajiaghayi, Anastasios Sidiropoulos, Morteza Zadimoghaddam
2008	J	`jnl`	Ordinal embeddings of minimum relaxation: General properties, trees, and ultrametrics. ACM Trans. Algorithms Noga Alon, Mihai Badoiu, Erik D. Demaine, Martin Farach-Colton, Mohammad Taghi Hajiaghayi, Anastasios Sidiropoulos
2008	J	`jnl`	Theory research at Google. SIGACT News Gagan Aggarwal, Nir Ailon, Florin Constantin, Eyal Even-Dar, Jon Feldman, Gereon Frahling, Monika Rauch Henzinger, S. Muthukrishnan, Noam Nisan, Martin Pál, Mark Sandler, Anastasios Sidiropoulos
2007	A*	`conf`	Approximation algorithms for embedding general metrics into trees. SODA Mihai Badoiu, Piotr Indyk, Anastasios Sidiropoulos
2007	—	`conf`	Probabilistic embeddings of bounded genus graphs into planar graphs. SCG Piotr Indyk, Anastasios Sidiropoulos
2006	A	`conf`	Convergence and Approximation in Potential Games. STACS George Christodoulou, Vahab S. Mirrokni, Anastasios Sidiropoulos
2006	—	`conf`	Embedding ultrametrics into low-dimensional spaces. SCG Mihai Badoiu, Julia Chuzhoy, Piotr Indyk, Anastasios Sidiropoulos
2006	J	`jnl`	On the Complexity of Processing Massive, Unordered, Distributed Data CoRR Jon Feldman, S. Muthukrishnan, Anastasios Sidiropoulos, Clifford Stein, Zoya Svitkina
2005	A*	`conf`	Approximation algorithms for low-distortion embeddings into low-dimensional spaces. SODA Mihai Badoiu, Kedar Dhamdhere, Anupam Gupta, Yuri Rabinovich, Harald Räcke, R. Ravi, Anastasios Sidiropoulos
2005	A*	`conf`	Low-distortion embeddings of general metrics into the line. STOC Mihai Badoiu, Julia Chuzhoy, Piotr Indyk, Anastasios Sidiropoulos
2005	A*	`conf`	Ordinal embeddings of minimum relaxation: general properties, trees, and ultrametrics. SODA Noga Alon, Mihai Badoiu, Erik D. Demaine, Martin Farach-Colton, Mohammad Taghi Hajiaghayi, Anastasios Sidiropoulos
2003	B	`conf`	Fractional and Integral Coloring of Locally-Symmetric Sets of Paths on Binary Trees. WAOA Ioannis Caragiannis, Christos Kaklamanis, Pino Persiano, Anastasios Sidiropoulos