Natural and Mathematical Sciences

Permanent URI for this collectionhttps://hdl.handle.net/10679/313

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Now showing 1 - 20 of 21

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Approximate markov-nash equilibria for discrete-time risk-sensitive mean-field games
(Informs, 2020-11) Saldı, Naci; Basar, T.; Raginsky, M.; Natural and Mathematical Sciences; SALDI, Naci
In this paper, we study a class of discrete-time mean-field games under the infinite-horizon risk-sensitive optimality criterion. Risk sensitivity is introduced for each agent (player) via an exponential utility function. In this game model, each agent is coupled with the rest of the population through the empirical distribution of the states, which affects both the agent's individual cost and its state dynamics. Under mild assumptions, we establish the existence of a mean-field equilibrium in the infinite-population limit as the number of agents (N) goes to infinity, and we then show that the policy obtained from the mean-field equilibrium constitutes an approximate Nash equilibrium when N is sufficiently large.
Open Access
B → T transition form factors in light-cone sum rules
(American Physical Society, 2019-11-11) Aliev, T. M.; Dağ, Hüseyin; Kokulu, A.; Ozpineci, A.; Natural and Mathematical Sciences; DAĞ, Hüseyin
We present a new calculation of the semileptonic tree-level and flavor-changing neutral current form factors describing B-meson transitions to tensor mesons T ¼ D2, K2, a2, f2 (JP ¼ 2þ). We employ the QCD light-cone sum rules approach with B-meson distribution amplitudes. We go beyond the leading-twist accuracy and provide analytically, for the first time, higher-twist corrections for the two-particle contributions up to twist-four terms. We observe that the impact of higher-twist terms to the sum rules is noticeable. We study the phenomenological implications of our results on the radiative B → K 2γ and semileptonic B → D 2lν¯l, B → K 2lþl− decays.
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Biocompatible MOFs for storage and separation of O2: A molecular simulation study
(American Chemical Society, 2019-02-27) Gülçay, Ezgi; Fındıkçı, İlknur Eruçar; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar; Gülçay, Ezgi
Metal organic frameworks (MOFs) are great candidates for capturing 02 due to their highly porous structures and tunable physical and chemical properties. In this study, we assessed the performance of 1525 biocompatible MOFs which have endogenous linkers and nontoxic metal centers for adsorption-based and membrane-based O-2 separation and also for high-pressure O-2 storage. We initially computed Henry's constants of O-2 and N-2 at zero coverage and 298 K by performing Grand Canonical Monte Carlo (GCMC) simulations and estimated infinite dilution adsorption selectivities for O-2/N-2 mixture. We performed binary mixture GCMC simulations for the top 15 candidates at various pressures and 298 K and compared mixture adsorption selectivities with those obtained from infinite dilution. We then estimated O-2 working capacities of 315 biocompatible MOFs obtained at 298 K and 140 bar for storage and 5 bar for release pressures. Our results showed that 15 biocompatible MOFs outperform gravimetric O-2 working capacities of the traditional adsorbent materials such as activated carbon and NaX and some common MOFs such as NU-125 and UMCM-152 at 298 K. We finally calculated O-2 and N-2 permeabilities and membrane selectivities of 45 promising MOF candidates for O-2/N-2 separation. Seventeen biocompatible MOF membranes were identified to exceed the Robeson's upper bound established for polymers. This computational study will be useful to identify the promising biocompatible MOFs for storage and separation of O-2. The bio-MOF library constructed in this study will also guide both experimental and computational studies for design and development of biocompatible MOFs for various medical applications.
Open Access
Charmed baryon spectrum from lattice QCD near the physical point
(American Physical Society, 2020-09-23) Bahtiyar, H.; Can, K. U.; Erkol, Güray; Gubler, P.; Oka, M.; Takahashi, T. T.; TRJQCD Collaboration; Natural and Mathematical Sciences; ERKOL, Güray
We calculate the low-lying spectrum of charmed baryons in lattice QCD on the 32(3) x 64, N-f = 2 +/- 1 PACS-CS gauge configurations at the almost physical pion mass of similar to 156 MeV/c(2). By employing a set of interpolating operators with different Dirac structures and quark-field smearings for the variational analysis, we extract the ground and first few excited states of the spin-1/2 and spin-3/2, singly, doubly, and triply charmed baryons. Additionally, we study the Xi(c)-Xi(c)' mixing and the operator dependence of the excited states in a variational approach. We identify several states that lie close to the experimentally observed excited states of the Sigma(c), Xi(c) and Omega(c) baryons, including some of the Xi(c) states recently reported by LHCb. Our results for the doubly and triply charmed baryons are suggestive for future experiments.
Open Access
Crucial topics in computer architecture education and a survey of textbooks and papers
(International Association of Engineers, 2020) Yıldız, A.; Gören, S.; Uğurdağ, Hasan Fatih; Aktemur, B.; Akdoğan, Taylan; Natural and Mathematical Sciences; Electrical & Electronics Engineering; UĞURDAĞ, Hasan Fatih; AKDOĞAN, Taylan
We have been teaching undergraduate computer architecture since 2012 in an unconventional way. Most undergraduate computer architecture courses are based on microprocessors, and they quickly move into advanced topics such as instruction pipelining, forwarding, branch prediction, cache, and even memory management unit. We instead spend only the last one-third of our course on these topics. The first two thirds of the course is devoted to microcontrollers, i.e., simple-minded processors with no memory hierarchy, no branch prediction, sometimes even no pipelining. Our claim is that it is very hard to truly grasp the advanced topics without full grasp of the basics. Equipped with the above approach, this article comes up with an all-inclusive list of crucial topics for computer architecture education, and it surveys 25 computer architecture textbooks as well as 38 computer architecture education papers to see how much they cover these topics. In addition to that, the article contains a concise description of the perspective of our course. One of the pillars of our course is a working CPU on FPGA. We have so far had around 600 students design their own unique CPUs using Verilog given a complete instruction set, close to 70% of them with complete success.
Open Access
Discrete-time average-cost mean-field games on Polish spaces
(TÜBİTAK, 2020) Saldı, Naci; Natural and Mathematical Sciences; SALDI, Naci
In stochastic dynamic games, when the number of players is sufficiently large and the interactions between agents depend on empirical state distribution, one way to approximate the original game is to introduce infinite-population limit of the problem. In the infinite population limit, a generic agent is faced with a so-called mean-field game. In this paper, we study discrete-time mean-field games with average-cost criteria. Using average cost optimality equation and Kakutani's fixed point theorem, we establish the existence of Nash equilibria for mean-field games under drift and minorization conditions on the dynamics of each agent. Then, we show that the equilibrium policy in the mean-field game, when adopted by each agent, is an approximate Nash equilibrium for the corresponding finite-agent game with sufficiently many agents.
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Electromagnetic properties of doubly charmed baryons in Lattice QCD
(Elsevier, 2013-11-04) Can, K. Utku; Erkol, Güray; Işıldak, Bora; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray; IŞILDAK, Bora; Can, K. Utku
We compute the electromagnetic properties of Ξcc baryons in (2+1)-flavor Lattice QCD. By measuring the electric charge and magnetic form factors of Ξcc baryons, we extract the magnetic moments, charge and magnetic radii as well as the ΞccΞccρ coupling constant, which provide important information to understand the size, shape and couplings of the doubly charmed baryons. We find that the two heavy charm quarks drive the charge radii and the magnetic moment of Ξcc to smaller values as compared to those of, e.g., the proton.
Unknown
Electromagnetic structure of charmed baryons in Lattice QCD
(Springer Science+Business Media, 2014-05) Can, Kadir Utku; Erkol, Güray; Işıldak, Bora; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray; IŞILDAK, Bora; Can, Kadir Utku
As a continuation of our recent work on the electromagnetic properties of the doubly charmed (sic)(cc) baryon, we compute the charge radii and the magnetic moments of the singly charmed Sigma(c), Omega(c) and the doubly charmed Omega(cc) baryons in 2+1 flavor Lattice QCD. In general, the charmed baryons are found to be compact as compared to the proton. The charm quark acts to decrease the size of the baryons to smaller values. We discuss the mechanism behind the dependence of the charge radii on the light valence- and sea-quark masses. The magnetic moments are found to be almost stable with respect to changing quark mass. We investigate the individual quark sector contributions to the charge radii and the magnetic moments. The magnetic moments of the singly charmed baryons are found to be dominantly determined by the light quark and the role of the charm quark is significantly enhanced for the doubly charmed baryons.
Unknown
Erratum to: Searches for long-lived charged particles in pp collisions at s√ = 7 and 8 TeV
(Springer, 2022-11-28) Chatrchyan, S.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
N/A
Unknown
The generalized fractional Benjamin–Bona–Mahony equation: Analytical and numerical results
(Elsevier, 2020-08) Oruc, G.; Borluk, Handan; Muslu, G. M.; Natural and Mathematical Sciences; BORLUK, Handan
The generalized fractional Benjamin-Bona-Mahony (gfBBM) equation models the propagation of small amplitude long unidirectional waves in a nonlocally and nonlinearly elastic medium. The equation involves two fractional terms unlike the well-known fBBM equation. In this paper, we prove local existence and uniqueness of the solutions for the Cauchy problem by using energy method. The sufficient conditions for the existence of solitary wave solutions are obtained. The Petviashvili method is proposed for the generation of the solitary wave solutions and their evolution in time is investigated numerically by Fourier spectral method. The efficiency of the numerical methods is tested and the relation between nonlinearity and fractional dispersion is observed by various numerical experiments.
Open Access
Hidden-beauty broad resonance Yb(10890) in thermal QCD
(Hindawi Limited, 2019) Süngü, J. Y.; Türkan, Arzu; Dağ, Hüseyin; Veliev, V.; Natural and Mathematical Sciences; TÜRKAN, Arzu; DAĞ, Hüseyin
In this work, the mass and pole residue of resonance Yb is studied by using QCD sum rules approach at finite temperature. Resonance Yb is described by a diquark-antidiquark tetraquark current, and contributions to operator product expansion are calculated by including QCD condensates up to dimension six. Temperature dependencies of the mass mYb and the pole residue Yb are investigated. It is seen that near a critical temperature (Tc similar or equal to 190MeV), the values of mYb and Yb decrease to 87% and to 44% of their values at vacuum.
Open Access
Light D-wave axial-tensor K2(1820) meson at finite temperature
(IOP Publishing, 2019-06) Türkan, Arzu; Dağ, Hüseyin; Süngü, J. Y.; Veliev, V.; Natural and Mathematical Sciences; TÜRKAN, Arzu; DAĞ, Hüseyin
In this work the properties of the axial-tensor K-2(1820) meson in a hot medium are investigated. The mass and the decay constant of this state are calculated via thermal QCD sum rules considering QCD condensates up to dimension five. Our analysis show that both mass and decay constant stay almost monotonous up to certain temperatures and then they diminish with increasing temperature. The mass and decay constant estimated at zero temperature are in good agreement with the present experimental data and theoretical estimations.
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Local existence of solutions to the initial-value problem for one-dimensional strain-limiting viscoelasticity
(Elsevier, 2020-11-15) Erbay, Hüsnü Ata; Erkip, A.; Şengül, Y.; Natural and Mathematical Sciences; ERBAY, Hüsnü Ata
In this work we prove local existence of strong solutions to the initial-value problem arising in one-dimensional strain-limiting viscoelasticity, which is based on a nonlinear constitutive relation between the linearized strain, the rate of change of the linearized strain and the stress. The model is a generalization of the nonlinear Kelvin-Voigt viscoelastic solid under the assumption that the strain and the strain rate are small. We define an initial-value problem for the stress variable and then, under the assumption that the nonlinear constitutive function is strictly increasing, we convert the problem to a new form for the sum of the strain and the strain rate. Using the theory of variable coefficient heat equation together with a fixed point argument we prove local existence of solutions. Finally, for several constitutive functions widely used in the literature we show that the assumption on which the proof of existence is based is not violated.
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Mean field multilayer stackelberg differential games in multi-agent systems
(Ministry Communications & High Technologies Republic Azerbaijan, 2018) Oner, A.; Gunel, G. O.; Saldı, Naci; Natural and Mathematical Sciences; SALDI, Naci
In this paper, we study linear-quadratic hierarchical mean field Stackelberg differential games with decentralized adapted open-loop information structure. In this game model, there are three levels of decision making, with a leader at the top level, sub-leaders at the intermediate level, and a large population of followers at lowest level. Accordingly, the leader cannot influence the followers' actions directly, but instead sub-leaders link up followers to the global leader as an intermediate layer. The leader plays a Stackelberg game with the sub-leaders, and the sub-leaders play a Stackelberg game of the mean field type with the followers. The followers are (weakly) coupled through a mean field term, which only affects the followers' individual costs. One of the contributions of this work is to consider the infinite population limit of the finite-follower multi-layer game model. We establish the existence of Stackelberg equilibrium in the limiting case, which is expected to be an approximate Stackelberg equilibrium by the law of large numbers when the population of followers is finite, but sufficiently large. We show the effectiveness of the proposed method through a numerical example.
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On the stability of solitary wave solutions for a generalized fractional Benjamin–Bona–Mahony equation
(IOP Publishing, 2022-03-03) Oruc, G.; Natali, F.; Borluk, Handan; Muslu, G. M.; Natural and Mathematical Sciences; BORLUK, Handan
In this paper we establish a rigorous spectral stability analysis for solitary waves associated to a generalized fractional Benjamin-Bona-Mahony type equation. Besides the well known smooth and positive solitary wave with large wave speed, we present the existence of smooth negative solitary waves having small wave speed. The spectral stability is then determined by analysing the behaviour of the associated linearized operator around the wave restricted to the orthogonal of the tangent space related to the momentum at the solitary wave. Since the analytical solution is not known, we generate the negative solitary waves numerically by using Petviashvili method. We also present some numerical experiments to observe the stability properties of solitary waves for various values of the order of nonlinearity and fractional derivative. Some remarks concerning the orbital stability are also celebrated.
Open Access
Radiative transitions of doubly charmed baryons in lattice QCD
(American Physical Society, 2018-12-13) Bahtiyar, H.; Can, K. U.; Erkol, Güray; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray
We evaluate the spin-3/2→spin-1/2 electromagnetic transitions of the doubly charmed baryons on 2+1 flavor, 323×64 PACS-CS lattices with a pion mass of 156(9) MeV/c2. A relativistic heavy quark action is employed to minimize the associated systematic errors on charm-quark observables. We extract the magnetic dipole, M1, and the electric quadrupole, E2, transition form factors. In order to make a reliable estimate of the M1 form factor, we carry out an analysis by including the effect of excited-state contributions. We find that the M1 transition is dominant and light degrees of freedom (u/d- or s-quark) play the leading role. E2 form factors, on the other hand, are found to be negligibly small, which in turn, have a minimal effect on the helicity and transition amplitudes. We predict the decay widths and lifetimes of Ξcc∗+,++ and Ωcc∗+ based on our results. Finite size effects on these ensembles are expected to be around 1%. Differences in kinematical and dynamical factors with respect to the Nγ→Δ transition are discussed and compared to nonlattice determinations while keeping possible systematic artifacts in mind. A comparison to Ωcγ→Ωc∗ transition and a discussion on systematic errors related to the choice of heavy quark action are also given. Results we present here are particularly suggestive for experimental facilities such as LHCb, PANDA, Belle II, and BESIII to search for further states.
Open Access
Top-quark forward-backward asymmetry from a color-octet t-channel resonance
(American Physical Society, 2014-05-09) Cheng, L.; Hayreter, Alper; Valencia, G.; Natural and Mathematical Sciences; HAYRETER, Alper
We consider new physics contributions to the top-quark forward-backward asymmetry from a neutral V-8(0) or charged V-8(+) color-octet vector exchanged in the t channel. We study the phenomenological constraints on these particles arising from the Tevatron and LHC7 measurements and compare them with those on their color-singlet counterparts Z' and W'. We find that the color octets fare better than the singlets in that they generate a lower A(C), a lower high-invariant mass cross section at LHC7 and a lower same sign top-pair cross section. However, they also generate a lower A(FB) than their color-singlet counterparts.
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Value iteration algorithm for mean-field games
(Elsevier, 2020-09) Anahtarcı, Berkay; Karıksız, Can Deha; Saldı, Naci; Natural and Mathematical Sciences; ANAHTARCI, Berkay; KARIKSIZ, Can Deha; SALDI, Naci
In the literature, existence of mean-field equilibria has been established for discrete-time mean field games under both the discounted cost and the average cost optimality criteria. In this paper, we provide a value iteration algorithm to compute stationary mean-field equilibrium for both the discounted cost and the average cost criteria, whose existence proved previously. We establish that the value iteration algorithm converges to the fixed point of a mean-field equilibrium operator. Then, using this fixed point, we construct a stationary mean-field equilibrium. In our value iteration algorithm, we use Q-functions instead of value functions.
Open Access
Vector and axial-vector couplings of D and D⁎ mesons in 2+1 flavor lattice QCD
(Elsevier, 2013-02-12) Can, Kadir Utku; Erkol, Güray; Oka, M.; Ozpineci, A.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray; Can, Kadir Utku
Using the axial-vector coupling and the electromagnetic form factors of the D and D⁎ mesons in 2+1 flavor lattice QCD, we compute the D⁎Dπ , DDρ and D⁎D⁎ρ coupling constants, which play an important role in describing the charm hadron interactions in terms of meson-exchange models. We also extract the charge radii of D and D⁎ mesons and determine the contributions of the light and charm quarks separately.
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Ξcγ→Ξc ′ transition in lattice QCD
(Elsevier, 2017-09-10) Bahtiyar, H.; Can, K. U.; Erkol, Güray; Oka, M.; Takahashi, T. T.; Natural and Mathematical Sciences; ERKOL, Güray
We evaluate the electromagnetic Ξcγ→Ξc ′ transition on 2+1 flavor lattices corresponding to a pion mass of ∼156 MeV. We extract the magnetic Sachs and Pauli form factors which give the Ξc–Ξc ′ transition magnetic moment and the decay widths of Ξc ′ baryons. We did not find a signal for the magnetic form factor of the neutral transition Ξc 0γ→Ξc ′0, which is suppressed by the U-spin flavor symmetry. As a byproduct, we extract the magnetic form factors and the magnetic moments of Ξc and Ξc ′ baryons, which give an insight to the dynamics of u/d, s and c quarks having masses at different scales.

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