Berker, Ahmet Nihat

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https://hdl.handle.net/20.500.12469/6148
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Nihat Berker A.
BERKER, Ahmet Nihat
Ahmet Nihat, Berker
Berker,Ahmet Nihat
Berker, AHMET NIHAT
A. Berker
B.,Ahmet Nihat
Berker,A.N.
Berker, A.
Berker, Ahmet Nihat
Berker N.
Ahmet Nihat Berker
Ahmet Nihat BERKER
Berker, A. N.
B., Ahmet Nihat
AHMET NIHAT BERKER
A. N. Berker
BERKER, AHMET NIHAT
Berker A.
Berker, A. Nihat
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Prof. Dr.
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[email protected]
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Electrical-Electronics Engineering
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Current Staff
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ORCID ID
0000-0002-5172-2172
Scopus Author ID
6701401118
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Google Scholar ID
WoS Researcher ID
AAC-6674-2020

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CLEAN WATER AND SANITATION6
CLEAN WATER AND SANITATION
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AFFORDABLE AND CLEAN ENERGY7
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DECENT WORK AND ECONOMIC GROWTH8
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INDUSTRY, INNOVATION AND INFRASTRUCTURE9
INDUSTRY, INNOVATION AND INFRASTRUCTURE
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Documents

160

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6800

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136

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6632

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Scholarly Output

32

Articles

32

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WoS Citation Count

124

Scopus Citation Count

130

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WoS Citations per Publication

3.88

Scopus Citations per Publication

4.06

Open Access Source

24

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JournalCount
Physical Review E17
Physica A: Statistical Mechanics and its Applications4
Physica A-Statistical Mechanics and Its Applications3
Chaos Solitons & Fractals2
Turkish Journal of Biology1
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  • Thumbnail Image
    Article
    XY-Ashkin Phase Diagram in D=3
    (Elsevier, 2025) Turkoglu, Alpar; Berker, A. Nihat
    The phase diagram of the Ashkin-Tellerized XY model in spatial dimension d = 3 is calculated by renormalization-group theory. In this system, each site has two spins, each spin being an XY spin, that is having orientation continuously varying in 2 pi radians. Nearest-neighbor sites are coupled by two-spin and four-spin interactions. The phase diagram has ordered phases that are ferromagnetic and antiferromagnetic in each of the spins, and phases that are ferromagnetic and antiferromagnetic in the multiplicative spin variable. The phase diagram distinctively exhibits a pair of symmetrically situated direct bifurcation points and a pair of symmetrically situated reverse bifurcation points of the phase boundaries. The renormalization-group flows are in terms of the doubly composite Fourier coefficients of the exponentiated energy of nearest-neighbor spins.
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    Article
    Citation - WoS: 14
    Citation - Scopus: 14
    Lower Lower-Critical Spin-Glass Dimension From Quenched Mixed-Spatial Spin Glasses
    (Amer Physical Soc., 2018) Atalay, Bora; Berker, A. Nihat
    By quenched-randomly mixing local units of different spatial dimensionalities we have studied Ising spin-glass systems on hierarchical lattices continuously in dimensionalities 1 <= d <= 3. The global phase diagram in temperature antiferromagnetic bond concentration and spatial dimensionality is calculated. We find that as dimension is lowered the spin-glass phase disappears to zero temperature at the lower-critical dimension d(c) = 2.431. Our system being a physically realizable system this sets an upper limit to the lower-critical dimension in general for the Ising spin-glass phase. As dimension is lowered towards d(c) the spin-glass critical temperature continuously goes to zero but the spin-glass chaos fully subsists to the brink of the disappearance of the spin-glass phase. The Lyapunov exponent measuring the strength of chaos is thus largely unaffected by the approach to d and shows a discontinuity to zero at d(c.)
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    Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Renormalization-Group Theory of the Heisenberg Model in D Dimensions
    (Elsevier, 2022) Tunca, Egemen; Berker, A. Nihat
    The classical Heisenberg model has been solved in spatial d dimensions, exactly in d = 1 and by the Migdal-Kadanoff approximation in d > 1, by using a Fourier-Legendre expansion. The phase transition temperatures, the energy densities, and the specific heats are calculated in arbitrary dimension d. Fisher's exact result is recovered in d = 1. The absence of an ordered phase, conventional or algebraic (in contrast to the XY model yielding an algebraically ordered phase) is recovered in d = 2. A conventionally ordered phase occurs at d > 2. This method opens the way to complex-system calculations with Heisenberg local degrees of freedom.(c) 2022 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Electric-field induced phase transitions in capillary electrophoretic systems
    (Aip Publishing, 2021) Kaygusuz, Hakan; Erim, F. Bedia; Berker, A. Nihat
    The movement of particles in a capillary electrophoretic system under electroosmotic flow was modeled using Monte Carlo simulation with the Metropolis algorithm. Two different cases with repulsive and attractive interactions between molecules were taken into consideration. Simulation was done using a spin-like system, where the interactions between the nearest and second closest neighbors were considered in two separate steps of the modeling study. A total of 20 different cases with different rates of interactions for both repulsive and attractive interactions were modeled. The movement of the particles through the capillary is defined as current. At a low interaction level between molecules, a regular electroosmotic flow is obtained; on the other hand, with increasing interactions between molecules, the current shows a phase transition behavior. The results also show that a modular electroosmotic flow can be obtained for separations by tuning the ratio between molecular interactions and electric field strength.
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    Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Fractal Measures of Sea, Lake, Strait, and Dam-Reserve Shores: Calculation, Differentiation, and Interpretation
    (ELSEVIER, 2021) Yılmazer, Dilara; Berker, A. Nihat; Yılmaz, Yücel
    The fractal dimensions d(f) of the shore lines of the Mediterranean, the Aegean, the Black Sea, the Bosphorus Straits (on both the Asian and European sides), the Van Lake, and the lake formed by the Ataturk Dam have been calculated. Important distinctions have been found and explained. (C) 2021 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Spin-S Spin-Glass Phases in the D=3 Ising Model
    (Amer Physical Soc, 2021) Artun, E. Can; Berker, A. Nihat
    All higher-spin (s >= 1/2) Ising spin glasses are studied by renormalization-group theory in spatial dimension d = 3, exactly on a d = 3 hierarchical model and, simultaneously, by the Migdal-Kadanoff approximation on the cubic lattice. The s-sequence of global phase diagrams, the chaos Lyapunov exponent, and the spin-glass runaway exponent are calculated. It is found that, in d = 3, a finite-temperature spin-glass phase occurs for all spin values, including the continuum limit of s -> infinity. The phase diagrams, with increasing spin s, saturate to a limit value. The spin-glass phase, for all s, exhibits chaotic behavior under rescalings, with the calculated Lyapunov exponent of lambda = 1.93 and runaway exponent of y(R) = 0.24, showing simultaneous strong-chaos and strong-coupling behavior. The ferromagnetic-spin-glass and spin-glass-antiferromagnetic phase transitions occurring, along their whole length, respectively at p(t) = 0.37 and 0.63 are unaffected by s, confirming the percolative nature of this phase transition.
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    Article
    Spin-Glass Phases and Multichaos in the Ashkin–Teller Model
    (Elsevier Ltd, 2026) Saray, A.; Berker, A.N.
    The global phase diagram of the Ashkin–Teller spin glass is calculated in d=3 spatial dimensions by renormalization-group theory. Depending on the value of the positive or negative four-spin interaction, qualitatively different topologies are found for the spin-glass phase diagram in the usual variables of temperature and fraction of antiferromagnetic nearest-neighbor interactions. Two different spin-glass phases occur. Both spin-glass phases are chaotic. One spin-glass exhibits phase reentrance that is reverse from the reentrances seen in previous spin-glass phase diagrams. Seven different phases: Ferromagnetic and antiferromagnetic, entropic ferromagnetic and entropic antiferromagnetic, spin-glass and entropic spin-glass, and disordered phases occur. The entropic ferromagnetic phase unusually but understandably occurs at temperatures above one spin-glass phase. A random disorder line is identified and no phase transition occurs on this line. Our calculation is exact on the d = 3 hierarchical lattice and Migdal–Kadanoff approximate on the cubic lattice. © 2025 Elsevier Ltd.
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    Article
    Metastable Potts droplets
    (AMER PHYSICAL SOC, 2021) Artun, E. Can; Berker, A. Nihat
    The existence and limits of metastable droplets have been calculated using finite-system renormalization-group theory, for q-state Potts models in spatial dimension d = 3. The dependence of the droplet critical sizes on magnetic field, temperature, and number of Potts states q has been calculated. The same method has also been used for the calculation of hysteresis loops across first-order phase transitions in these systems. The hysteresis loop sizes and shapes have been deduced as a function of magnetic field, temperature, and number of Potts states q. The uneven appearance of asymmetry in the hysteresis loop branches has been noted. The method can be extended to criticality and phase transitions in metastable phases, such as in surface-adsorbed systems and water.
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    Article
    Merged Potts-Clock Model: Algebraic and Conventional Multistructured Multicritical Orderings in Two and Three Dimensions
    (Amer Physical Soc, 2023) Artun, E. Can; Berker, A. Nihat
    A spin system is studied with simultaneous permutation-symmetric Potts and spin-rotation-symmetric clock interactions in spatial dimensions d = 2 and 3. The global phase diagram is calculated from the renormalization-group solution with the recently improved (spontaneous first-order detecting) Migdal-Kadanoff approximation or, equivalently, with hierarchical lattices with the inclusion of effective vacancies. Five different ordered phases are found: Conventionally ordered ferromagnetic, quadrupolar, antiferromagnetic phases and algebraically ordered antiferromagnetic, antiquadrupolar phases. These five different ordered phases and the disordered phase are mutually bounded by first-and second-order phase transitions, themselves delimited by multicritical points: Inverted bicritical, zero-temperature bicritical, tricritical, second-order bifurcation, and zero-temperature highly degenerate multicritical points. One rich phase diagram topology exhibits all of these phenomena.
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    Article
    Multiplicity of Algebraic Order From Fixed Lines of Potential Surfaces: X-Y-Ashkin in Spatial Dimension D=2
    (Amer Physical Soc, 2025) Artun, E.C.; Berker, A.N.
    A position-space renormalization-group study is done for the Ashkin-Tellerized XY model, as an exact solution on the d=2 hierarchical lattice and an approximate solution on the square lattice. A multiplicity of algebraic order is found in the phase diagram, in the form of renormalization-group fixed lines composed of a continuous sequence of interaction potential surfaces. In the Ashkin-Tellerized XY model, each site has two continuously varying spins, each spin being an XY spin, that is, having orientation continuously varying in 2π radians. Nearest-neighbor sites are coupled by two-spin and four-spin interactions. The phase diagram has algebraically ordered phases that are ferromagnetic and antiferromagnetic in each of the spins, and algebraically ordered phases that are ferromagnetic and antiferromagnetic in the combined spin variable. These phases are subtended by fixed lines of potential surfaces that are multiplicatively different Berezinskii-Kosterlitz-Thouless fixed potentials. The evolution of continuously varying criticality is traced within each of the four phases. The renormalization-group flows, the fixed lines, and the interaction surfaces are in terms of the doubly composite Fourier coefficients of the exponentiated energy of the four nearest-neighbor spins. The disordered phase is maintained along two semi-infinite a priori quasi-disorder lines. This record is sourced from MEDLINE/PubMed, a database of the U.S. National Library of Medicine