Julia Komjathy


     Hello visitor!
     This is my fairly minimalistic website, up-to-date on 14 April 2022.
     I am an associate professor at the TU Delft in the Applied Probability group.




     My address:                

     Delft University of Technology
     Department Elektrotechniek, Wiskunde en Informatica (EWI)
     Delft Institute of Applied Mathematics (DIAM)
     Applied Probability Group
     Mekelweg
     2628CD Delft
     The Netherlands

      email: J.[Last name] at tudelft dot nl,
      office phone: not really known to me...
     EWI building, room 7.050

This picture is about 10 years old now..., about to be replaced.

Research interests
     
  • random graph models of complex networks
         
  • spatial random graphs, hyperbolic random graphs
         
  • topology and structure of weighted random graphs
         
  • `explosion' in weighted random graphs
         
  • epidemic spread on networks
         
  • branching processes


    Current news that might interest you:

    I am organising the probability seminar, here is our current list of speakers: Seminar Series in Probabillity and Statistics at TU Delft

    I am organising this workshop coming up on 3--7 Oct 2022, send us an email if you are interested:
    Recent Trends in Spatial Stochastic Processes


    Phd students, postdocs
         
  • Enrico Baroni. Thesis: Universality of weighted scale-free configuration model
          jointly with Remco van der Hofstad, award date: 6 Feb 2017
          [ link to thesis at Tue library ]
         
  • Viktoria Vadon. Thesis: Random intersection graphs
          jointly with Remco van der Hofstad, award date: June 16 2020
          [ link to thesis at Tue library ]
         
  • Daniel Olah. Thesis: Reliable geometric spanners
          jointly with Kevin Buchin, award date: 10 July 2021
          [ link to thesis at Tue library ]
         
  • Joost Jorritsma: Distances and components in scale-free random graph models
          graduation date: expected 2023 Jan
         
  • Zsolt Bartha: postdoc. Topic: Contact processes and k-cores.
         
    Links to other websites that I find interesting

    Recent highlights

    1.       G. Odor, D. Czifra, J. Komjathy, L. Lovasz, and M. Karsai
            Switchover phenomenon induced by epidemic seeding on geometric networks
            Proceedings of the National Academy of Sciences,
            (PNAS), Vol 118 (41) 118 (41) e2112607118 (2021)
            [ journal ] [ arXiv ]
            Short description: This Covid-inspired paper investigates the effect of the initial seeding of an epidemic on the final outbreak size. Starting an epidemic from the best-connected nodes of a network would intuitively lead to the largest outbreak. We challenge this picture and show that: Epidemics started from the central part of a geometric metapopulation network can reach more individuals only if the basic reproduction number is small, but if the epidemic is more infectious, it reaches a larger population when seeded from uniformly selected nodes. We show that spatial geometry amplifies this effect in both data-driven and synthetic epidemic models, and we give mathematical proofs that this phenomenon appears in various random graph models. These results help us understand why real epidemics started from seemingly similar conditions may have significantly different outcomes.

    2.       J. Jorritsma, and J. Komjathy
            Distance evolutions in growing preferential attachment graphs (2022)
            Annals of Applied Probability, online first (2022)
            [ journal ] [ arXiv ]
            Short description: This paper is the first to study how graph (and weighted) distances in preferential attachment-type models shrink as the graph grows around two vertices chosen uniformly at random at some time t. It shows that the graph-distance stays in a tight strip around the main order term for all later times, and eventually settles on 2.

    3.       J. Komjathy and B. Lodewijks
            Explosion in weighted Hyperbolic Random Graphs and Geometric Inhomogeneous Random Graphs (2020)
            Stochastic Processes and their Applications Vol. 130(3), pages 1309-1367 (2020)
            [ journal ] [ arXiv ]
            Short description: This paper is the first to study first passage percolation on scale-free spatial networks: geometric inhomogeneous random graphs (GIRG), scale-free percolation (SFP) and hyperbolic random graphs (HRG). It identifies the precise criterion for explosion, which is valid whenever there is doubly-exponential ball-growth in the model. This paper also provides a unifying framework to treat spatial models with a so-called product-kernel (GIRG, SFP, HRG) all at once, and describes the weak local limit of GIRGs and HRGs.

    Full list of publications and preprints

          up to date on 14 April 2022
    1.       Z. Bartha, J. Komjathy, J. Raes
            Sharp bound on the threshold metric dimension of trees
           [ arXiv ]

    2.       J. Jorritsma, and J. Komjathy
            Distance evolutions in growing preferential attachment graphs (2022)
            Annals of Applied Probability, online first (2022)
            [ journal ]       [ arXiv ]

    3.       R. van der Hofstad, J. Komjathy and V. Vadon
            Phase transition in random intersection graphs with communities (2022)
            Random Structured and Algorithms Vol. 60, Issue 3, 406-461 (2022)
            [ journal ] [ arXiv ]

    4.       G. Odor, D. Czifra, J. Komjathy, L. Lovasz, and M. Karsai
            Switchover phenomenon induced by epidemic seeding on geometric networks
            Proceedings of the National Academy of Sciences,
            (PNAS), Vol 118 (41) 118 (41) e2112607118 (2021)
            [ journal ] [ arXiv ]

    5.       L. A. Goldberg, J. Jorritsma, J. Komjathy, and J. Lapinskas
            Increasing efficacy of contact-tracing applications by user referrals and stricter quarantining (2021)
            PLoS One, 16 (5): e0250435 (2021)
            [ journal ] [ medRXiv ]

    6.       R. van der Hofstad, J. Komjathy and V. Vadon
            Random Intersection Graphs with Communities
            Advances in Applied Probability online first (Nov 2021)
            [ journal ] [ arXiv ]

    7.       J. Komjathy, J. Lapinskas and J. Lengler
            Stopping explosion by penalising transmission to hubs in scale-free spatial random graphs (2021)
            Annales de l'Institute Henri Poincare, Vol. 57 (4) p:1968-2016, (Nov 2021)
           [ journal ] [ arXiv ]

    8.       J. Komjathy, and G. Odor
            The metric dimension of critical Galton-Watson trees and linear preferential attachment trees (2021)
            European Journal of Combinatorics Vol 95, pages 103317, (June 2021)
            [ journal ] [ arXiv ]

    9.       J. Jorritsma, T. Hulshof and J. Komjathy
            Not all interventions are equal for the height of the second peak (2020)
            Chaos, Solitons \& Fractals Vol. 139: 109965 (2020)
            [ journal ] [ arXiv ]

    10.       J. Jorritsma, and J. Komjathy
            Weighted distances in scale-free preferential attachment models (2020)
            Random Structures and Algorithms, Vol 57 (3): 823-859 (2020)
            [ journal ] [ arXiv ]

    11.       J. Komjathy and B. Lodewijks
            Explosion in weighted Hyperbolic Random Graphs and Geometric Inhomogeneous Random Graphs (2020)
            Stochastic Processes and their Applications Vol. 130(3), pages 1309-1367 (2020)
            [ journal ] [ arXiv ]

    12.       V. Vadon, J. Komjathy and R. van der Hofstad
            A new model for overlapping communities with arbitrary internal structure
            Applied Network Science, Vol 4:42 (2019)
            [ journal ]

    13.       J. Komjathy, R. Molontay and K. Simon
            Transfinite fractal dimension of trees and hierarchical scale-free graphs
            Journal of Complex Networks, cnz005 (2019)
            [ journal ] [ arXiv ]

    14.       E. Baroni and R. van der Hofstad and J. Komjathy
            Tight fluctuations of weight-distances in random graphs with infinite-variance degrees
            Journal of Statistical Physics Vol 174, Issue 4, pp 906 - 934 (2019)
            [ journal ] [ arXiv ]

    15.       E. Adriaans and J. Komjathy
            Weighted distances in scale free configuration models
      Journal of Statistical Physics Vol 173 (3) p: 1082 -- 1109 (2018)
            [ journal ] [ arXiv ]

    16.       R. van der Hofstad and J. Komjathy
            Explosion and distances in scale-free percolation (2017 June)
            [ arXiv ]

    17.       K. Simon, S. Molnar, J. Komjathy, P. Mora
            Large Deviation Multifractal Analysis of a Process Modeling TCP CUBIC (2017 June)
            [ arXiv ]

    18.       R. van der Hofstad and J. Komjathy
            When is a scale-free graph ultra-small?
            Journal of Statistical Physics Vol. 169 (2), pp 223 - 264, (2017).
            [ journal ] [ arxiv ]

    19.       E. Baroni and R. van der Hofstad and J. Komjathy
            Non-universality of weighted random graphs with infinite variance degrees
            Journal of Applied Probability Vol 54, Issue 1 p. 146 - 164 (2017)
            [ arXiv ] [ journal ]

    20.       J. Komjathy
            Explosion of Crump-Mode-Jagers branching processes (2016 Feb)
            [ arXiv ]

    21.       J. Komjathy and V. Vadon
            First passage percolation on the Newman-Watts small world model
            Journal of Statistical Physics, vol. 162, Issue 4, p. 959-993 (2016)
            [ arXiv ] [ journal ]

    22.       J. Komjathy:
            Fixed speed competition on the configuration model with infinite variance degrees: equal speeds (2015 Mar)
            [ arXiv ]

    23.       E. Baroni and R. v. d. Hofstad and J. Komjathy:
            Fixed speed competition on the configuration model with infinite variance degrees: unequal speeds
            Electronic Journal of Probability, vol 20. no. 116, p. 1-48 (2015)
            [ arXiv] [ journal ]

    24.       S. Bhamidi and R. v. d. Hofstad and J. Komjathy:
            The front of the epidemic curve and first passage percolation,
            Journal of Applied Probability, vol. 51A p. 101-121 2014.
            [ arXiv ] [ journal ]

    25.       I. Kolossvary and J. Komjathy and L. Vago:
            Degrees and distances in random and evolving Apollonian networks
            Advances in Applied Probability, vol. 48, no. 3 p. 865-902. 2016.
            [ arXiv ] [ journal ]

    26.       S. Bhamidi and J. Goodman and R. v. d. Hofstad and J. Komjathy:
            Degree distribution of shortest path trees and bias of network sampling algorithms,
            Annals of Applied Probability vol. 25, no. 4, p. 1780-1826. (2015)
            [ arXiv ] [ journal ]

    27.       J. Komjathy and Y. Peres:
            Topics in Markov chains: Mixing and escape rate
            Proceedings of Symposia in Pure Mathematics, Volume 91, (2016)
            (Probability and Statistical Physics in St. Petersburg)
            [ arXiv ] [ journal ]

    28.       I. Kolossvary and J. Komjathy:
           First passage percolation on inhomogeneous random graphs,
           Advances of Applied Probability vol 47 No. 2 p. 589-610. (2015)
            [ arXiv ] [ journal ]

    29.       J. Komjathy and Y. Peres:
            Mixing and relaxation time for random walk on wreath product graphs,
            Electronic Journal of Probability, vol. 18, 71, p. 1-23, (2013)
            [ arXiv ] [ journal ]

    30.       J. Komjathy and J. Miller and Y. Peres:
            Uniform mixing time for random walk on lamplighter graphs,
            Annales de l'Institute Henri Poincare, vol. 50, (Number 4) p. 1140-1160 (2014)
            [ arXiv ] [ journal ]

    31.       J. Komjathy and K. Simon:
            Generating hierarchical scale free graphs from fractals,
            Chaos, Solitons and Fractals, vol. 44, p. 651-666, (2011)
            [ arXiv ] [ journal ]

    32.       M. Balazs and J. Komjathy and T. Seppalainen:
            Fluctuation bounds in the exponential bricklayers process,
            Journal of Statistical Physics, vol. 147, no. 1, p. 35-62, 2012
            [ journal ]

    33.       M. Balazs and J. Komjathy and T. Seppalainen:
            Microscopic concavity and fluctuation bounds in a class of deposition processes,
            Annales de l'Institute Henri Poincare vol. 48, no.1, p. 151-187, 2012
            [ journal ]

    34.       M. Balazs and J. Komjathy:
            Order of current variance and diffusivity in the rate one totally asymmetric zero range process
            Journal of Statistical Physics vol. 133, (1), pp 59-78, 2008
            [ journal ]
    Edited Proceedings
           
    1. D. Gleich, J. Komjathy, and N. Litvak:
            Algorithms and Models for the Web Graph
            12th International Workshop, 12th International Workshop,
            WAW 2015, Eindhoven, The Netherlands, December 10-11, 2015, Proceedings (Springer)
            [ journal ]


    Thesis

    I defended my Phd in Dec 2012, under the supervision of Marton Balazs and Karoly Simon:       This is my thesis (pdf).

          A 24 page summary of my thesis (pdf).

    CV

          CV (updated 2021 May)