Krzysztof Klosin


Krzysztof Klosin
Department of Mathematics
Queens College CUNY
65-30 Kissena Blvd
Queens, NY 11367, USA
Email: kklosin(at)qc(dot)cuny(dot)edu
Tel: +1 718 997 5833



I am a professor in the Department of Mathematics at Queens College of the City University of New York (CUNY) and a member of the doctoral faculty at the Graduate Center of CUNY. I received my Ph.D. from the University of Michigan in 2006. My thesis advisor was Chris Skinner. Thanks to two of my students Vivian Kuang and Rochelle Luong I now know that I have an Erdös number of 3.

My other academic affiliations:
  1. Princeton University (Visiting Research Scholar 2017-2018)
  2. Max Planck Institute for Mathematics, Bonn (Guest Researcher 2010, 2011)
  3. Université Paris 13 (Postdoc 2009-2010)
  4. Cornell University (Visiting Assistant Professor 2008-2009)
  5. University of Utah (Burgess Assistant Professor 2006-2008)
Click here for my detailed CV. My research is supported by the Travel Support for Mathematicians - MP-TSM-00002098 Grant from the Simons Foundation (2023-2028) and by the PSC-CUNY Research Award TradB-55-45 (2024-2025).

If you are a student and are looking for my YouTube channel, click here.


The Graduate Center Arithmetic Geometry Seminar

I am a co-organizer (along with Heidi Goodson) of the Graduate Center Arithmetic Geometry Seminar which meets on (some) Tuesdays 3-4pm at the Graduate Center. Anyone interested in attending is welcome to stop by or join in by zoom.

Ph.D. students

Joe Kramer-Miller - graduated May 2016 from the CUNY Graduate Center. Postdoctoral positions at the University College London and at UC Irvine. Currently an Assistant Professor at Lehigh University.

Lawrence Vu - graduated September 2019 from the CUNY Graduate Center. His thesis was published in J. Number Theory 198 (2019), 250-292.

Geoffrey Akers - currently a Ph.D. student at the CUNY Graduate Center.

Xiaoyu (Coco) Huang - graduated May 2024 from the CUNY Graduate Center. Her thesis was published in Kyoto J. Math. Currently a postdoc at Temple University.

Research

My research is in algebraic number theory. More specifically I am interested in: the Bloch-Kato conjecture for modular forms, congruences among automorphic forms on GL(2) and higher-rank groups, modularity of Galois representations, special values of L-functions, the Paramodular Conjecture.

Papers/preprints

(The versions below may differ slightly from the published versions. Please, contact me for the latest versions of the papers.)
  1. R=T theorems for weight one modular forms (with T. Berger), Trans. Amer. Math. Soc., 376(2023) no.11, 8095–8128.

  2. Irreducibility of limits of Galois representations of Saito-Kurokawa type (with T. Berger), Res. Number Theory, 7(3):Paper No. 41, 25, (2021). Open access article: here

  3. Deformations of Saito-Kurokawa type and the Paramodular Conjecture (with T. Berger, appendix by C. Poor, J. Shurman, D. S. Yuen), Amer. J. Math. 142 (2020), no. 6, 1821-1876.

  4. Galois extensions and a conjecture of Ogg (with M. Papikian), Proc. Amer. Math. Soc. 148 (2020), 3821-3834.

  5. Congruence primes for automorphic forms on unitary groups and applications to the arithmetic of Ikeda lifts (with J. Brown), Kyoto J. Math. 60 (2020), no. 1, 179-217.

  6. Modularity of residual Galois extensions and the Eisenstein ideal (with T. Berger), Trans. Amer. Math. Soc. 372 (2019), no. 11, 8043-8065.

  7. A p-adic Hermitian Maass lift (with T. Berger), Glasg. Math. J. 61 (2019), no. 1, 85–114.

  8. On Ribet's isogeny for J_0(65) (with M. Papikian), Proc. Amer. Math. Soc. 146 (2018), no. 8, 3307–3320.

  9. On the action of the U_p operator on the local (at p) representation attached to congruence level Siegel modular forms (with J. Brown), Ramanujan J. 44 (2017), no. 3, 597–615.

  10. On lifting and modularity of reducible residual Galois representations over imaginary quadratic fields (with T. Berger), Int. Math. Res. Not. IMRN (2015), no. 20, 10525–10562. (There is an error in the proof of Lemma 4.6. This makes the statements pertaining to the existence of a modular basis (as in Corollary 4.8) conditional upon the conclusion of that lemma. This also impacts some statements made in [5] above. We will post a correction here soon.)

  11. Maass spaces on U(2,2) and the Bloch-Kato conjecture for the symmetric square motive of a modular form, J. Math. Soc. Japan, Vol. 67, No. 2 (2015) pp. 797-860. This version contains more details than the published version.

  12. On higher congruences between automorphic forms (with T. Berger, K. Kramer), Math. Res. Lett., 21 (2014), no. 1, 71-82.

  13. A note on Hecke eigenvalues of hermitian Siegel Eisenstein series, Ramanujan J., 35 (2014), no. 2, 287-298. The final publication is available here.

  14. On deformation rings of residually reducible Galois representations and R=T theorems (with T. Berger), Math. Ann., 355 (2013), no. 2, 481-518. The original publication is available at www.springerlink.com - click here to access the published version).

  15. On Ihara's lemma for degree one and two cohomology over imaginary quadratic fields, Int. J. Number Theory, 09 (2013), 1541-1561.

  16. Yoshida lifts and the Bloch-Kato conjecture for the convolution L-function (with M. Agarwal), J. Number Theory, 133 (2013), 2496-2537.

  17. An R=T theorem for imaginary quadratic fields (with T. Berger), Math. Ann., 349 (2011), no. 3, 675-703. The original publication is available at www.springerlink.com - click here to access the published version).

  18. A deformation problem for Galois representations of imaginary quadratic fields (with T. Berger), J. Inst. Math. Jussieu, (2009) 8(4), 669-692 . (copyright to the linked document held by Cambridge University Press). .

  19. Congruences among modular forms on U(2,2) and the Bloch-Kato conjecture, Ann. Inst. Fourier (Grenoble), 59 no. 1 (2009), p. 81-166).

  20. Ihara's lemma for imaginary quadratic fields, J. Number Theory, 128 (2008), 2251-2262.



Some recent and upcoming talks:

  1. Colloquium (Oliver Club), Cornell University, November 9, 2023.

  2. AMS Fall Eastern Sectional Meeting, Special session on Homological Aspects of p-adic Groups and Automorphic Representations, University at Buffalo, September 9, 2023.

  3. Lehigh Algebraic/Arithmetic Geometry Seminar, Lehigh University, November 11, 2022.

  4. Joint Columbia-CUNY-NYU Number Theory Seminar, CUNY Graduate Center, November 3, 2022.

  5. AMS Fall Eastern Sectional Meeting, Special session on Iwasawa Theory, University of Massachusetts-Amherst, October 1, 2022.

  6. Workshop on Eisenstein Series, L-functions, and arithmetic, University of Pittsburgh, May 18, 2022.

  7. Philadelphia Area Number Theory Seminar, Bryn Mawr College, November 4, 2021.

  8. Number Theory Seminar, University of California, Irvine, May 13, 2020. Zoom link: https://uci.zoom.us/j/98027654087

  9. Topology, Geometry and Physics Seminar, CUNY Graduate Center, New York, September 25, 2019.

  10. Arithmetic Algebraic Geometry Seminar, University of A. Mickiewicz, Poznan, Poland, August 6, 2019.

  11. Conference on p-adic families of automorphic forms and Galois representations, University of Sheffield, UK, July 15-19, 2019.

  12. AMS Sectional Meeting, University of Connecticut, Hartford, CT, April 13-14, 2019.

  13. 33rd Automorphic Forms Workshop, Duquesne University, Pittsburgh, PA, March 6-10, 2019.

  14. Arithmetic Algebraic Geometry Conference, Poznan, Poland, August 26 - September 1, 2018.

  15. Connecticut Summer School in Number Theory Conference, University of Connecticut, June 2, 2018, at 3:20 pm.

  16. Algebra and Number Theory Seminar, Pennsylvania State University, April 26, 2018, at 11:00 am.

  17. 32nd Automorphic forms Workshop, Tufts University, March 19-22, 2018.

  18. Philadelphia Area Number Theory Seminar, Bryn Mawr College, December 6, 2017, at 2:40 pm.

  19. Number Theory Seminar, University of Sheffield, UK, August 3, 2017 at 2:00 pm.

  20. Colloquium, University of A. Mickiewicz, Poznan, Poland, July 20, 2017 at 12:00 pm.

  21. Algebra and Number Theory Seminar, Pennsylvania State University, May 4, 2017, at 11:00 am.

  22. 2nd International Conference on Galois Representations and Automorphic Forms, The Banach Conference Center, Bedlewo, Poland, July 19, 2016 at 10:10 am.

  23. Number Theory Seminar, University of Sheffield, UK, July 21, 2016 at 2:00 pm.

  24. 30th Automorphic forms Workshop, Wake Forest University, NC, March 8, 2016 at 10 am.

  25. Workshop on Bianchi and Siegel modular forms, Sheffield, UK, July 16, 2014 at 11:00 am.

  26. Building Bridges: 2nd EU-US conference on Automorphic Forms and related topics , Bristol, UK, July 9, 2014 at 9:30 am.

  27. 28th Automorphic forms Workshop, Moab, UT, May 12, 2014 at 3:30 pm.

  28. Algebra and Number Theory Seminar, Pennsylvania State University, March 6, 2014, at 11:15 am.

  29. Number Theory Seminar, University of North Carolina at Chapel Hill, November 5, 2013, at 3:30 pm.

  30. Algebra and Number Theory Seminar, Universitat Heidelberg, July 26, 2013, at 1:30 pm.

  31. Colloquium, Universitat Heidelberg, July 25, 2013, at 5:00 pm.

  32. Number theory seminar, University of California at San Diego, January 14, 2013, at 2 pm.

  33. Automorphic forms and representation theory seminar, Purdue University, October 25, 2012 at 1:30 pm.

  34. Number theory seminar, University of Sheffield, UK, August 13, 2012 at 11:00 am.

  35. Building Bridges: 1st EU-US conference on Automorphic Forms and related topics , Aachen, Germany, August 8, 2012 at 4:40 pm.

  36. Algebraic K-theory and arithmetic conference, The Banach Center, Bedlewo, Poland, July 25, 2012 at 3:00 pm.

  37. ESI Programme on Automorphic Forms: Arithmetic and Geometry, Vienna, Austria, January 17, 2012.

  38. Number Theory seminar, Clemson University, December 1, 2011 at 3:30 pm.

  39. Galois Representations and Automorphic Forms - conference talk, The Banach Center, Bedlewo, Poland, August 17, 2011 at 2:20 pm.

  40. Number theory lunch seminar, Max-Planck-Institut fuer Mathematik, Bonn, July 20, 2011 at 2:15 pm.

  41. Number theory seminar, University of Sheffield, UK, June 29, 2011 at 1:10 pm.

  42. Colloquium, Szczecin University, Szczecin, Poland, January 20, 2011 at 4:00 pm.

  43. Seminaires de l'equipe d'Arithmetique et Geometrie Algebrique, Universite Paris Nord, January 7, 2011 at 10:30 am.

  44. Colloquium, University of A. Mickiewicz, Poznan, Poland, December 22, 2010 at 12:00 pm.

  45. Collaborative Number Theory Seminar at the CUNY Graduate Center, CUNY, November 19, 2010 at 4:00 pm.

  46. Number Theory seminar, Northwestern University, November 1, 2010 at 2:00 pm.

  47. Colloquium, CUNY Queens College, October 5.

  48. Oberseminar (Algebra, Geometrie und Zahlentheorie), University of Duisburg-Essen, June 1, 2010 at 4:15 pm.

  49. Number Theory Seminar, DPMMS, University of Cambridge, March 9, 2010 at 2:30 pm.

  50. Seminaire Arithmetique et geometrie algebrique, Universite Louis Pasteur Strasbourg, February 22, 2010 at 4:00 pm.

  51. Seminaires de l'equipe d'Arithmetique et Geometrie Algebrique, Universite Paris Nord, November 6, 2009 at 10:30 am.

  52. Seminaire de theorie des nombres de Chevaleret, Universite Paris 6 et 7, October 26, 2009 at 2:00 pm.



Expository articles/talks

  1. On the norms of p-stablized elliptic newforms (with Jim Brown with appendix by Keith Conrad).

  2. Congruences among automorphic forms on unitary groups and the Bloch-Kato conjecture (pdf) - slides from my talk at the Joint Meeting of the AMS in San Diego (January 2008).

  3. Some local (at p) properties of residual Galois representations (dvi, pdf) - presented at the 2005-06 Number Theory Learning Seminar on the Serre's conjecture at the University of Michigan.

  4. On the reflex norm (dvi, pdf) - presented in the 2004-2005 VIGRE Number Theory Working Group on complex multiplication of abelian varieties at the University of Michigan.

  5. On variations of Hodge structures - presented at the 2002 Arizona Winter School on "Periods" (with J. Brown, Kirsten Eisentrager, Jorge Pineiro, Mak Trifkovich, Oliver Watson, supervised by Prof. Johan deJong).

  6. Finiteness of Mordell-Weil (dvi, pdf) - presented in the 2003-2004 VIGRE Number Theory Working Group on torsion points of elliptic curves over Q at the University of Michigan.

  7. Application of Mordell-Weil finiteness (dvi, pdf) - presented in the 2003-2004 VIGRE Number Theory Working Group on torsion points of elliptic curves over Q at the University of Michigan.



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