** **

#### Education:

Ph.D., Mathematics, Brown University

M.Sc., Mathematics, Brown University

B.Sc., Mathematics, University of Cyprus

**Research Interests: **

Partial differential equations of mixed type; nonlinear hyperbolic conservation laws; kinetic theory; nonlinear diffusive-dispersive equations; differential geometry

** **

**Courses Taught at WVU:**

Math 758. Theory of Partial Differential Equations 2

Math 757. Theory of Partial Differential Equations 1

Math 651. Real Variables 2

Math 568. Advanced Calculus

Math 567. Advanced Calculus

Math 566. Intermediate Partial Differential Equations

Math 560. Introduction to Dynamical Systems and Applications

Math 555. Complex Variables 1

Math 551. Real Variables 1

Math 465. Partial Differential Equations

Math 460. Introduction to Dynamical Systems and Applications

Math 456. Complex Variables

Math 451. Introduction to Real Analysis 1

Math 375. Applied Modern Algebra

Math 261. Elementary Differential Equations

Math 251. Multivariable Calculus

Math 155. Calculus 1

**Recent Publications:**

Radially Symmetric Non-isentropic Euler flows: continuous blowup with positive pressure, Helge Kristian Jenssen and Charis Tsikkou, arXiv:2211.04309 (2022)

Amplitude Blowup in Radial Isentropic Euler Flow, Helge Kristian Jenssen and Charis Tsikkou, SIAM Journal on Applied Mathematics, 80 (2020), no. 6, 2472-2495. MR4181105

Multi-d isothermal Euler flow: existence of unbounded radial similarity solutions, Helge Kristian Jenssen and Charis Tsikkou, Physica D. Nonlinear Phenomena, 410 (2020), 132511, 14 pp. MR4091348

On similarity flows for the compressible Euler system, Helge Kristian Jenssen and Charis Tsikkou, Journal of Mathematical Physics, 59 (2018), no. 12, 121507, 25. pp. MR3894017

Riemann Problems for the Nonlinear Wave System: Rarefaction Wave Interactions, Eun Heui Kim and Charis Tsikkou, Discrete and Continuous Dynamical Systems, 37 (2017), no. 12, 6257-6289. MR3690303

Radial solutions to the Cauchy problem for $\square_{1+3}U=0$ as limits of exterior solutions, Helge Kristian Jenssen and Charis Tsikkou, Journal of Hyperbolic Differential Equations, 13 (2016), no. 4, 833-860. MR3593709

**Grants:**

(with Casian Pantea) Mathematical Association of America's Dolciani Mathematics Enrichment Grant Program. Title: West Virginia University Junior Math Club. Co-Principal Investigator. April 2021 - May 2023. Amount: $5,000

NSF, DMS - 1714912, Applied Mathematics. Title: Solutions of Nonlinear Hyperbolic and Mixed Type Partial Differential Equations. Principal Investigator. July 15, 2017 - June 30, 2022. Amount: $141,000

(with Casian Pantea) WVU Internal Grants Program, Community Engagement. Title: WVU Junior Math Club. Co-Principal Investigator. October 1, 2016 - May 31, 2017. Amount: $5,526

(with Casian Pantea) Mathematical Association of America's Dolciani Mathematics Enrichment Grant Program. Title: West Virginia University Junior Math Club. Co-Principal Investigator. March 20, 2015 - May 31, 2017. Amount: $6,000

(with Adrian Tudorascu) NSF, DMS - 1400168, Applied Mathematics, Analysis Program, Award DMS-1400168. Title: Entropy and Singular Solutions for Conservation Laws; Pressureless Gas Dynamics and other applications. Co-Principal Investigator. May 1, 2014 - April 30, 2016. Amount: $37,000

WVU Internal award by the WVU ADVANCE Sponsorship Program, funded by NSF Advance-Institution Transformation, CLB-Advance-IT program under the Award HRD-1007978. Title: Symmetric Solutions to Hyperbolic Conservation Laws. Principal Investigator. October 1, 2014 - December 31, 2015. Amount: $15,000

**Recent Talks: **

40th Southeastern-Atlantic Regional Conference on Differential Equations, North Carolina State University, Raleigh, Department of Mathematics, November 12-13, 2022

PDE Seminar, The Ohio State University, Columbus, Department of Mathematics, October 11, 2022

Joint Mathematics Meetings. Special Session: “Partial Differential Equations and Complex Variables”, April 9, 2022

PDE Seminar, University of Houston, Houston, Department of Mathematics, March 25, 2022

AMS-MAA Joint Mathematics Meetings. Special Session: “Partial Differential Equations and Spaces of Holomorphic Functions”, January 8, 2021

**Outreach:**

Organized the WVU Integration Bee, a mathematical competition open to all WVU and local high school students, Springs of 2014-2015 (with Casian Pantea), Springs of 2016-2018 (with Casian Pantea and Adrian Tudorascu), Spring of 2019 (with Casian Pantea, Galyna Voitiuk and Iwona Wojciechowska), Spring of 2022 (with Ela Celikbas and Adrian Tudorascu)

Organized (with Casian Pantea) the WVU Junior Math Competition, a mathematical competition for high-school students, Spring 2017

Organized (with Casian Pantea) the WVU Junior Math Club, a program of weekly Olympiad problem sessions for high-school students in the Morgantown, WV area, September 2014-April 2017