Berker, Ahmet Nihat

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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.
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AHMET NIHAT BERKER
A. N. Berker
BERKER, AHMET NIHAT
Berker A.
Berker, A. Nihat
Job Title
Prof. Dr.
Email Address
nihatberker@khas.edu.tr
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Electrical-Electronics Engineering
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Website
ORCID ID
0000-0002-5172-2172
Scopus Author ID
6701401118
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WoS Researcher ID
AAC-6674-2020
Scholarly Output

27

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27

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0

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0

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2021 - 20234
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Subject: Renormalization

Scholarly Output Search Results

Now showing 1 - 4 of 4
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    Article
    Citation - WoS: 8
    Citation - Scopus: 8
    First-order to second-order phase transition changeover and latent heats of q-state Potts models in d=2,3 from a simple Migdal-Kadanoff adaptation
    (Amer Physical Soc, 2022) Berker, Ahmet Nihat; Berker, A. Nihat
    The changeover from first-order to second-order phase transitions in q-state Potts models is obtained at q(c) = 2 in spatial dimension d = 3 and essentially at q(c) = 4 in d = 2, using a physically intuited simple adaptation of the Migdal-Kadanoff renormalization-group transformation. This simple procedure yields the latent heats at the first-order phase transitions. In both d = 2 and 3, the calculated phase transition temperatures, respectively compared with the exact self-duality and Monte Carlo results, are dramatically improved. The method, when applied to a slab of finite thickness, yields dimensional crossover.
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    Article
    Citation - WoS: 6
    Citation - Scopus: 6
    Lower Critical Dimension of the Random-Field Xy Model and the Zero-Temperature Critical Line
    (Amer Physical Soc, 2022) Akin, Kutay; Berker, Ahmet Nihat; Berker, A. Nihat
    The random-field XY model is studied in spatial dimensions d = 3 and 4, and in between, as the limit q -> infinity of the q-state clock models, by the exact renormalization-group solution of the hierarchical lattice or, equivalently, the Migdal-Kadanoff approximation to the hypercubic lattices. The lower critical dimension is determined between 3.81 < d(c) < 4. When the random field is scaled with q, a line segment of zero-temperature criticality is found in d = 3. When the random field is scaled with q(2), a universal phase diagram is found at intermediate temperatures in d = 3.
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    Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Phase Transitions of the Variety of Random-Field Potts Models
    (Elsevier, 2021) Turkoglu, Alpar; Berker, Ahmet Nihat; Berker, A. Nihat
    The phase transitions of random-field q-state Potts models in d = 3 dimensions are studied by renormalization-group theory by exact solution of a hierarchical lattice and, equivalently, approximate Migdal-Kadanoff solutions of a cubic lattice. The recursion, under rescaling, of coupled random-field and random-bond (induced under rescaling by random fields) coupled probability distributions is followed to obtain phase diagrams. Unlike the Ising model (q = 2), several types of random fields can be defined for q >= 3 Potts models, including random-axis favored, random-axis disfavored, random-axis randomly favored or disfavored cases, all of which are studied. Quantitatively very similar phase diagrams are obtained, for a given q for the three types of field randomness, with the low-temperature ordered phase persisting, increasingly as temperature is lowered, up to random-field threshold in d = 3, which is calculated for all temperatures below the zero-field critical temperature. Phase diagrams thus obtained are compared as a function of q. The ordered phase in the low-q models reaches higher temperatures, while in the high-q models it reaches higher random fields. This renormalization-group calculation result is physically explained. (c) 2021 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Nematic Ordering in the Heisenberg Spin-Glass System in Three Dimensions
    (Amer Physical Soc, 2023) Tunca, Egemen; Berker, Ahmet Nihat; Berker, A. Nihat
    Nematic ordering, where the spins globally align along a spontaneously chosen axis irrespective of direction, occurs in spin-glass systems of classical Heisenberg spins in d = 3. In this system where the nearest-neighbor interactions are quenched randomly ferromagnetic or antiferromagnetic, instead of the locally randomly ordered spin-glass phase, the system orders globally as a nematic phase. This nematic ordering of the Heisenberg spin -glass system is dramatically different from the spin-glass ordering of the Ising spin-glass system. The system is solved exactly on a hierarchical lattice and, equivalently, Migdal-Kadanoff approximately on a cubic lattice. The global phase diagram is calculated, exhibiting this nematic phase, and ferromagnetic, antiferromagnetic, disordered phases. The nematic phase of the classical Heisenberg spin-glass system is also found in other dimensions d > 2: We calculate nematic transition temperatures in 24 different dimensions in 2 < d 4.