
 
 
 Efficient Spectral Algorithms for Massive and Dynamic Graphs is an EPSRC Fellowship awarded to He Sun (EP/T00729X/1). The fellowship studies advances of spectral graph theory, designs efficient spectral   algorithms for massive and dynamic graphs, and develops an open-source library of spectral algorithms for graphs. With a total award of 1,507,133 pounds, the Fellowship runs from 2020 to 2025, and the current team consists of the PI, 1 Postdocs,  3 PhD students, and 1 Research Interns.   
 He Sun, Principal Investigator 
 
                 
                 
 John Stewart Fabila Carrasco, Postdoctoral Researcher  
                  
  Joyentanuj Das, Postdoctoral Researcher  
                 
  Ben Jourdan, PhD Student    
                 
  Steinar Laenen, PhD Student      
                 
Suranjan De, PhD Student

As part of the Fellowship, we are developing STAG, an open-source library of efficient spectral algorithms for graphs. STAG is the first such algorithmic library mainly written in C++, with a python wrapper around the underlying C++ library for python users. The source code of STAG can be found from our GitHub page, and will be updated actively. More information can be also found from the STAG website.
 Signed Laplacians for Constrained Graph Clustering. with John Stewart Fabila Carrasco (ICML'25, Spotlight). 
          
 Dynamic Similarity Graph Construction with Kernel Density Estimation. with Steinar Laenen, and Peter Macgregor (ICML'25). 
           arXiv version | Code
  
          
 Online Sparsification of  Bipartite-Like Clusters in Graphs. with Joyentanuj Das, and Suranjan De (ICML'25). 
          
 Coreset Spectral Clustering. with Ben Jourdan, Gregory Schwartzman, and Peter Macgregor (ICLR'25). 
          	       Conference version | arXiv version | Code
          
 Can We Measure the Impact of a Database?
              with P. Buneman, D. Dosso, M. Lissandrini, and G. Silvello. Communications of the ACM, May 2025. 
          	      Journal version |  arXiv version 
          
 Dynamic Spectral Clustering with Provable Approximation Guarantee. 
              with S. Laenen (ICML'24). 
              Conference version | arXiv version | Code
          	     
          
Polynomial-Time Algorithms for Weaver's Discrepancy Problem in a Dense Regime.   
          with B. Jourdan, and P. Macgregor.
                      arXiv version   
      	  
 Fast Approximation of Similarity Graphs with Kernel Density Estimation. 
              with P. Macgregor (NeurIPS'23, Spotlight). 
 
                 Conference version |  arXiv version | Code
        
               
Fast and Simple Spectral Clustering in Theory and Practice. P. Macgregor (NeurIPS'23).
 Three Hardness Results for Graph Similarity Problems. with D. Vagnozzi. submitted 
          arXiv version 
         	
      	  
 Nearly-Optimal Hierarchical Clustering for Well-Clustered Graphs. 
              with B. Manghiuc and S. Laenen (ICML'23). 
 
               Conference version | arXiv version | Talk | Code
         	 
          
The Support of Open versus Closed Random Walks.  
          with T. Sauerwald, and D. Vagnozzi (ICALP'23). 
          Conference version 
                     
      	 	 
Is the Algorithmic Kadison-Singer Problem Hard?            with B. Jourdan, and P. Macgregor (ISAAC'23).
                      arXiv version     	     
Fully-Dynamic Graph Sparsifiers Against an Adaptive Adversary. 
          	with A. Bernstein, J. van den Brand, M. Gutenberg, D. Nanongkai, T. Saranurak, and A. Sidford (ICALP'22). 
          	 Conference version |
                      arXiv version       	 
 A Tighter Analysis of Spectral Clustering, and Beyond.
              with P. Macgregor (ICML'22).
              Conference version |
         	 arXiv version | Talk  | 
		Code
             
          
 Hierarchical clustering: O(1)-approximation for well-clustered graphs. 
              with B. Manghiuc (NeurIPS'21). 
 
         	 Conference version |  
         	 arXiv version | Talk |
		Code
            
          
Finding bipartite components in hypergraphs. 
	   with P. Macgregor (NeurIPS'21). 
 
	 		Conference version |  
	 		arXiv version | Talk | 
	 		Code
                      
      	
 Local algorithms for finding densely connected clusters. 
              with P. Macgregor (ICML'21 for a long talk). 
                    Conference version | 
                    arXiv version |  
		    Talk | 
		    Code
          
 Higher-order spectral clustering of directed graphs. 
              with S. Laenen (NeurIPS'20). 
          	    Conference version |  
          	    arXiv version |  
		    Talk  
          
Augmenting the Algebraic Connectivity of Graphs. 
   	 with B. Manghiuc, and P. Peng (ESA'20) 
                       Conference version | 
                       arXiv version  
    	
 Hermitian matrices for clustering directed graphs: insights and applications. 
              with M. Cucuringu, H. Li, and L. Zanetti (AISTATS'20). 
                   Conference version | 
                   arXiv version