ABOUT

The Research Center for Logic, Optimization and Security (LOS) was founded in October 2020 by Laurenţiu Leuştean (head), Paul Irofti and Andrei Pătraşcu.
Our main objective is to stimulate interdisciplinary research in the fields of logic, optimization and security. We are interested both in fundamental research as well as in industrial applications. We focus on proof mining and applications to optimization, ergodic theory and nonlinear analysis, convex optimization for machine learning, signal processing and matrix factorization (dictionary learning), security, anomaly detection and anti-money laundry.

Contact
Hall 317, Faculty of Mathematics and Computer Science,
Academiei 14, 010014 Bucharest, Romania
Email: los@fmi.unibuc.ro

PEOPLE

Faculty


Associated researchers


PhD Students


Undergraduate and Master Students

Vladimir Antofi

VLADIMIR ANTOFI

Alexandru Scânteie

ALEXANDRU SCÂNTEIE

DAFINA TRUFAŞ



Former Members

SEMINARS

Scientific seminars organized by LOS members

LOS SEMINAR

The working seminar of the LOS research center.

LOGIC SEMINAR

The seminar features talks on mathematical logic, philosophical logic and logical aspects of computer science.




PROOF MINING SEMINAR

The seminar presents recent results on proof mining.



Past seminars

PUBLICATIONS

Journal papers

  1. P. Firmino, L. Leuștean, Rates of (T-)asymptotic regularity of the generalized Krasnoselskii-Mann-type iteration, Portugaliae Mathematica (Online First) (2025)
    DOI: 10.4171/pm/2148
  2. L. Romero-Ben, P. Irofti, F. Stoican, V. Puig, Dual Unscented Kalman Filter Architecture for Sensor Fusion in Water Networks Leak Localization, IEEE Transactions on Control Systems Technology (Early Access), pp. 1-12 (2025)
    DOI: 10.1109/TCST.2025.3610975
  3. A. Sipoş, The computational content of super strongly nonexpansive mappings and uniformly monotone operators, Israel Journal of Mathematics (2025)
    DOI: 10.1007/s11856-025-2824-0
  4. H. Cheval, L. Leuștean, Linear rates of asymptotic regularity for Halpern-type iterations, Mathematics of Computation 94:1323-1333 (2025)
    DOI: 10.1090/mcom/3991
  5. P. Firmino, L. Leuștean, Quantitative asymptotic regularity of the VAM iteration with error terms for accretive operators in Banach spaces, Zeitschrift für Analysis und ihre Anwendungen 44(3/4):501-519 (2025)
    DOI: 10.4171/ZAA/1772
  6. M. Prunescu, On other two representations of the C-recursive integer sequences by terms in modular arithmetic, Journal of Symbolic Computation 130:102433 (2025)
    DOI: 10.1016/j.jsc.2025.102433
  7. M. Prunescu, L. Sauras-Altuzarra, Computational considerations on the representation of number-theoretic functions by arithmetic terms, Journal of Logic and Computation 35(3):exaf012 (2025)
    DOI: 10.1093/logcom/exaf012
  8. M. Prunescu, L. Sauras-Altuzarra, On the representation of C-recursive integer sequences by arithmetic terms, Journal of Difference Equations and their Applications 31(9):1263–1285 (2025)
    DOI: 10.4171/pm/2148
  9. H. Cheval, Rates of asymptotic regularity of the Tikhonov-Mann iteration for families of mappings, 69(3-4):415-431 (2024)
    DOI: 10.59277/RRMPA.2024.415.431
  10. P. Irofti, L. Romero-Ben, F. Stoican, V. Puig Learning Dictionaries from Physical-Based Interpolation for Water Network Leak Localization, IEEE Transactions on Control Systems Technology 32(3):755-766 (2024)
    DOI: 10.1109/TCST.2023.3329696
  11. L. Leuştean, P. Pinto, Rates of asymptotic regularity for the alternating Halpern-Mann iteration, Optimization Letters 18:529-543 (2024)
    DOI: 10.1007/s11590-023-02002-y
  12. M. Prunescu, L. Sauras-Altuzarra An arithmetic term for the factorial function, Examples and Counterexamples, 5:100136 (2024)
    DOI: 10.1016/j.exco.2024.100136
  13. L. Romero-Ben, P. Irofti, F. Stoican, V. Puig Head Estimation through Unscented Kalman Filter for Data-driven Leak Localization in Water Networks, IFAC-PapersOnLine 58(4):67-72 (2024)
    DOI: 10.1016/j.ifacol.2024.07.195
  14. A. Sipoș, On quantitative metastability for accretive operators , Zeitschrift für Analysis und ihre Anwendungen 43(3/4):417-433 (2024)
    DOI: 10.4171/zaa/1741
  15. H. Cheval, U. Kohlenbach, L. Leuştean, On modified Halpern and Tikhonov-Mann iterations, Journal of Optimization Theory and Applications 197:233-251 (2023)
    DOI: 10.1007/s10957-023-02192-6
  16. L. Păunescu, A. Sipoş, A proof-theoretic metatheorem for tracial von Neumann algebras, Mathematical Logic Quarterly, 69(1):63-76 (2023)
    DOI: 10.1002/malq.202200048
  17. H. Cheval, L. Leuştean, Quadratic rates of asymptotic regularity for the Tikhonov-Mann iteration, Optimization Methods and Software (2022)
    DOI: 10.1080/10556788.2022.2060974
  18. S.S. Mihai, F. Stoican, B.D. Ciubotaru, On the link between explicit MPC and the face lattice of the lifted feasible domain, IFAC-PapersOnLine 55(16):308-313 (2022)
    DOI: 10.1016/j.ifacol.2022.09.042
  19. T.G. Nicu, F. Stoican, I. Prodan, Polyhedral potential field constructions for obstacle avoidance in a receding horizon formulation, IFAC-PapersOnLine 55(16):254-259 (2022)
    DOI: 10.1016/j.ifacol.2022.09.033
  20. A. Pătrașcu, P. Irofti, On finite termination of an inexact Proximal Point algorithm, Applied Mathematics Letters 134:108348 (2022)
    DOI: 10.1016/j.aml.2022.108348
  21. M. Prunescu, Symmetries in the Pascal triangle: $p$-adic valuation, sign-reduction modulo $p$ and the last non-zero digit, Bulletin Mathématique de la Société des Sciences Mathématiques de Roumanie 65(4):431-447 (2022)
  22. C. Rusu, C. Rosasco, Fast approximation of orthogonal matrices and application to PCA, Signal Processing 194:108451 (2022)
    DOI: 10.1016/j.sigpro.2021.108451
  23. A. Sipoș, Abstract strongly convergent variants of the proximal point algorithm, Computational Optimization and Applications 83:349-380 (2022)
    DOI: 10.1007/s10589-022-00397-5
  24. A. Sipoș, On extracting variable Herbrand disjunctions, Studia Logica 110:1115–1134 (2022)
    DOI: 10.1007/s11225-022-09990-5
  25. A. Sipoş, Quantitative inconsistent feasibility for averaged mappings, Optimization Letters 16:1915–1925 (2022)
    DOI: 10.1007/s11590-021-01812-2
  26. A. Sipoş, Revisiting jointly firmly nonexpansive families of mappings, Optimization 71:3819-3834 (2022)
    DOI: 10.1080/02331934.2021.1915312
  27. L. Leuștean, P. Pinto, Quantitative results on a Halpern-type proximal point algorithm, Computational Optimization and Applications 79:101–125 (2021)
    DOI: 10.1007/s10589-021-00263-w
  28. A. Pătrașcu, P. Irofti, Stochastic proximal splitting algorithm for composite minimization, Optimization Letters 15:2255–2273 (2021)
    DOI: 10.1007/s11590-021-01702-7
  29. C. Rusu, An iterative coordinate descent algorithm to compute sparse low-rank approximations, IEEE Signal Processing Letters 29:249-253 (2021)
    DOI: 10.1109/LSP.2021.3132276
  30. C. Rusu, L. Rosasco, Constructing fast approximate eigenspaces with application to the fast graph Fourier transforms, IEEE Transactions on Signal Processing 69:5037-5050 (2021)
    DOI: 10.1109/TSP.2021.3107629
  31. A. Sipoş, A quantitative multiparameter mean ergodic theorem, Pacific Journal of Mathematics 314(1):209-218 (2021)
    DOI: 10.2140/pjm.2021.314.209
  32. A. Sipoș, Bounds on strong unicity for Chebyshev approximation with bounded coefficients, Mathematische Nachrichten 294(12):2425–2440 (2021)
    DOI: 10.1002/mana.201900439
  33. A. Sipoș, Construction of Fixed Points of Asymptotically Nonexpansive Mappings in Uniformly Convex Hyperbolic Spaces, Numerical Functional Analysis and Optimization 42:696-711 (2021)
    DOI: 10.1080/01630563.2021.1924780
  34. A. Sipoș, Rates of metastability for iterations on the unit interval, Journal of Mathematical Analysis and Applications 502:125235 (2021)
    DOI: 10.1016/j.jmaa.2021.125235


Conference/workshop papers

  1. A. Dușa and P. Irofti, CCubes: a quasi-polynomial, exact Boolean minimizer, 34th International Workshop on Logic and Synthesis, IEEE, pp. 1-7 (2025)
  2. D. Trufaş, Intuitionistic Propositional Logic in Lean, Proceedings Eighth Symposium on Working Formal Methods (FROM 2024), Timişoara, Romania, September 16-18, Electronic Proceedings in Theoretical Computer Science 410, pp. 133–149 (2024)
    DOI: 10.4204/EPTCS.410.9
  3. R. Bălucea, P. Irofti, Software Mitigation of RISC-V Spectre Attacks, Innovative Security Solutions for Information Technology and Communications. SecITC 2023, Lecture Notes in Computer Science 14534. Springer, Cham, pp. 51-64 (2023)
    DOI: 10.1007/978-3-031-52947-4_5
  4. P. Irofti, Pinky: A Modern Malware-oriented Dynamic Information Retrieval Tool, Innovative Security Solutions for Information Technology and Communications. SecITC 2023, Lecture Notes in Computer Science 14534. Springer, Cham, pp. 65-78 (2023)
    DOI: 10.1007/978-3-031-52947-4_6
  5. A. Stancu, P. Irofti, I. Leuștean, OpenBSD formal driver verification with SeL4, Innovative Security Solutions for Information Technology and Communications. SecITC 2023, Lecture Notes in Computer Science 14534. Springer, Cham, pp. 144-156 (2023)
    DOI: 10.1007/978-3-031-52947-4_11
  6. P. Irofti, L. Romero-Ben, F. Stoican, V. Puig, Data-driven Leak Localization in Water Distribution Networks via Dictionary Learning and Graph-based Interpolation, 2022 IEEE Conference on Control Technology and Applications (CCTA), Trieste, Italy, pp. 1265-1270 (2022)
    DOI: 10.1109/CCTA49430.2022.9966160
  7. P. Irofti, A. Pătrașcu, A.I Hîji, Unsupervised Abnormal Traffic Detection through Topological Flow Analysis, 2022 14th International Conference on Communications (COMM), Bucharest, Romania, pp. 1-6 (2022)
    DOI: 10.1109/COMM54429.2022.9817285
  8. P. Irofti, C. Rusu, A. Pătraşcu, Dictionary Learning with Uniform Sparse Representations for Anomaly Detection, ICASSP 2022 - 2022 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Singapore, Singapore, pp. 3378-3382 (2022)
    DOI: 10.1109/ICASSP43922.2022.9747365
  9. I. Leuștean, B. Macovei, DELP: Dynamic Epistemic Logic for Security Protocols, 2021 23rd International Symposium on Symbolic and Numeric Algorithms for Scientific Computing (SYNASC), Timișoara, Romania, pp. 275-282 (2021)
    DOI: 10.1109/SYNASC54541.2021.00053
  10. C. Rusu, P. Irofti, Efficient and Parallel Separable Dictionary Learning, 2021 IEEE 27th International Conference on Parallel and Distributed Systems (ICPADS), Beijing, China, pp. 380-386 (2021)
    DOI: 10.1109/ICPADS53394.2021.00053


Preprints

  1. A. Apostu, S.F Gheorghe, A. Hîji, N. Cleju, A. Pătraşcu, C. Rusu, R.T. Ionescu, P. Irofti, Detecting and Mitigating DDoS Attacks with AI: A Survey, arXiv:2503.17867 [cs.CR] (2025)
  2. I.P. Ciobanu, A.I. Hîji, N.C. Ristea, P. Irofti, C. Rusu, R.T. Ionescu, XMAD-Bench: Cross-Domain Multilingual Audio Deepfake Benchmark, arXiv:2506.00462 [cs.SD] (2025)
  3. A.V. Costache, S.F. Gheorghe, E.G. Poesina, P. Irofti, R.T. Ionescu, A Survey of Text Classification Under Class Distribution Shift, arXiv:2502.12965 [cs.CL] (2025)
  4. P. Irofti, L. Romero-Ben, F. Stoican, V. Puig, Factor Graph Optimization for Leak Localization in Water Distribution Networks, arXiv:2509.10982 [eess.SY] (2025)
  5. L. Leuștean, Notes on applicative matching logic, arXiv:2506.10088 [cs.LO] (2025)
  6. L. Leuștean, D. Trufaș, Matching logic - a new axiomatization, arXiv:2506.13801 [cs.LO] (2025)
  7. M.Prunescu, Arithmetic closed forms count the Mersenne primes, the Fermat primes and the twin-prime pairs, arXiv:2512.01680 [math.NT] (2025)
  8. M.Prunescu, On polynomial systems of equations in square matrices filled with natural numbers, arXiv:2507.15265 [math.LO] (2025)
  9. M.Prunescu, Polynomial fingerprinting for trees and formulas, arXiv:2506.21114 [math.LO] (2025)
  10. M. Prunescu, L. Sauras-Altuzarra, J. Shunia, A Minimal Substitution Basis for the Kalmar Elementary Functions, arXiv:2505.23787 [math.LO] (2025)
  11. M.Prunescu, J. M. Shunia, Elementary closed-forms for non-trivial divisors, arXiv:2510.26939 [math.NT] (2025)
  12. M. Prunescu, J. Shunia, On modular representations of C-recursive integer sequences, arXiv:2502.16928 [math.NT] (2025)
  13. L. Romero-Ben, P. Irofti, F. Stoican, V. Puig, A comparison between joint and dual UKF implementations for state estimation and leak localization in water distribution networks, arXiv:2510.24228 [eess.SY] (2025)
  14. A. Sipoș, On the uniform convexity of the squared distance, arXiv:2503.03442 [math.MG] (2025)
  15. H. Cheval, Quantitative metastability of the Tikhonov-Mann iteration for countable families of mappings, arXiv:2406.03429 [math.OC] (2024)
  16. C. Cobeli, M. Prunescu, A. Zaharescu, On non-holonomicity, transcendence and $p$-adic valuations, arXiv:2412.16517 [math.NT] (2024)
  17. F.-A. Croitoru, A.-I. Hîji, V. Hondru, N.C. Ristea, P. Irofti, M. Popescu, C. Rusu, R.T. Ionescu, F.S. Khan, M. Shah, Deepfake Media Generation and Detection in the Generative AI Era: A Survey and Outlook, arXiv:2411.19537 [cs.CV] (2024)
  18. P. Irofti, I.A. Hîji, A. Pătrașcu, N. Cleju, Fusing Dictionary Learning and Support Vector Machines for Unsupervised Anomaly Detection, arXiv:2404.04064 [cs.LG] (2024)
  19. A. Pătrașcu, C. Rusu, P. Irofti, Learning Explicitly Conditioned Sparsifying Transforms, arXiv:2403.03168 [math.NA] (2024)
  20. P. Pinto, A. Sipoș, Products of hyperbolic spaces, arXiv:2408.14093 [math.MG] (2024)
  21. M. Prunescu, J. Shunia, Arithmetic-term representations for the greatest common divisor, arXiv:2411.06430 [math.NT] (2024)
  22. M. Prunescu, J. Shunia, On arithmetic terms expressing the prime-counting function and the n-th prime, arXiv:2412.14594 [math.NT] (2024)
  23. A. Pătrașcu, P. Irofti, Computational complexity of Inexact Proximal Point Algorithm for Convex Optimization under Holderian Growth, arXiv:2108.04482 [cs.LG] (2021)
  24. C. Rusu, An iterative Jacobi-like algorithm to compute a few sparse eigenvalue-eigenvector pairs, arXiv:2105.14642 [math.NA] (2021)

PROJECTS

Profet (680PED/2022)

The project PROFET aims at developing and implementing a better solution compared to the existing ones regarding the precise positioning of a satellite onto its orbit. The efficiency of our approach comes from the low frequency of interaction between the space object and the GNSS (Global Navigation Satellite System) network. To achieve this, the definition of mission requirements, altogether with data retrieval from the orbital satellite is needed. The successful design of the estimation algorithms will be followed by the definition of the hardware requirements and the design of an electronic module, the estimation software being implemented at the firmware level, afterwards.

NetAlert (SOL4/2021)

NetAlert aims to create a hardware-software sensor solution for detecting anomalies in computer networks based on the monitoring and analysis of data packets. The network-mounted sensor will provide real-time alerts on abnormal traffic behaviors using two complementary approaches:
(i) static analysis based on rules and behavioral patterns;
(ii) machine learning (ML) analysis without prior expert knowledge.






DDNET (12PD/2020)

The main goal of this project, called DDNET, is to adapt and propose new dictionary learning methods for solving untractable fault detection and isolation problems found in distribution networks. Given a large dataset of sensor measurements from the distribution network, the dictionary learning algorithms should be able to produce the subset of network nodes where faults exist.










Graphomaly (287PED/2020)

The proposed project, called Graphomaly, aims to create a Python software package for anomaly detection in graphs that model financial transactions, with the purpose of discovering fraudulent behavior like money laundering, illegal networks, tax evasion, scams, etc. Such a toolbox is necessary in banks, where fraud detection departments still use mostly human experts.



StOpAnomaly (143PD/2020)

StOpAnomaly aims to create, analyze and implement numerical optimization algorithms for large-scale optimization focusing on robust anomaly detection models based on decomposition and one-class classification. The research will be directed towards development of a toolbox containing scalable stochastic algorithms that can be used to detect several classes of anomalies in noisy large datasets.