arXiv subjects

Ekrem Aydiner

Publications and source records attributed to Ekrem Aydiner.

35 records · Page 2Linked to original sources

arXiv2015

Damped Oscillating Dark Energy: Ideal Fluid and Scalar-Tensor description

In this paper, we study damped oscillating form of dark energy for explaining dynamics of universe. First of all, we consider universe is filled with an ideal fluid which has damped oscillating dark energy in terms of this case we calculate several physical quantities such as Hubble parameter, acceleration parameter, energy density, pressure and others for dark energy, dark energy-matter coupling and non-coupling cases. Secondly, we consider as universe is filled with scalar field instead of an ideal fluid we obtain these physical quantities in terms of scalar potential and kinetic term for the same cases in scalar-tensor formalism. Finally, we show that ideal fluid description and scalar-tensor description of dark energy give mathematically equivalent results for this EoS parameter, even if they haven't same physical meaning.

gr-qc↗

arXiv2015

Oscillating Casimir force of trapped Bose gas in electromagnetic field

In this study, we consider motion of the massive and charged Bose gas trapped in electric and magnetic fields between two parallel plates in the $x-y$ plane that are separated by a distance $d$ in the $z$ direction. We derive analytical expression of the grand canonical potential of the quantum particles by using of Ketterle and van Druten approximation. By evaluating canonical potential, we obtain Casimir potential and force at the Bose-Einstein condensation temperature $T_{c}$. We also show that Casimir force oscillates depends on distance $d$ for fixed parameters.

quant-ph↗

arXiv2015

Casimir force for geometrically confined ideal Bose gas in a harmonic-optical potential

In this study, we have derived close form of the Casimir force for the non-interacting ideal Bose gas between two slabs in harmonic-optical lattice potential by using Ketterle and van Druten approximation. We find that Bose-Einstein condensation temperature $T_{c}$ is a critical point for different physical behavior of the Casimir force. We have shown that Casimir force of confined Bose gas in the presence of the harmonic-optical potential decays with inversely proportional to $d^{5}$ when $T\leq T_{c}$. However, in the case of $T>T_{c}$, it decays exponentially depends on separation $d$ of the slabs. Additionally we have discussed temperature dependence of Casimir force and importance of the harmonic-optical lattice potential on quantum critical systems, quantum phase transition and nano-devices.

quant-ph↗

arXiv2013

Thermal entanglement in the mixed three spin XXZ Heisenberg Model on a triangular cell

We numerically investigate thermal entanglement of the spins (1/2,1) and (1/2,1/2) in the three-mixed (1/2,1,1/2) anisotropic Heisenberg XXZ spin system on a simple triangular cell under an inhomogeneous magnetic field. We show that the external magnetic field induces strong plateau formation in pairwise thermal entanglement for fixed parameters of Hamiltonian in the case of the ferromagnetic and anti-ferromagnetic interactions. We also observe an unexpected critical point at finite temperature in the thermal entanglement of the spins (1/2,1) for antiferromagnetic case while the entanglement of the spins (1/2,1) for ferromagnetic case and the entanglement of the spins (1/2,1/2) for both ferromagnetic and antiferromagnetic cases almost decays exponentially to zero with increasing temperature. The critical point in entanglement of the spins (1/2,1) for antiferromagnetic case may be signature of the quantum phase transition at finite temperature.

cond-mat.stat-mech↗

arXiv2011

Survival probability in a one-dimensional quantum walk on a trapped lattice

The dynamics of the survival probability of quantum walkers on a one-dimensional lattice with random distribution of absorbing immobile traps are investigated. The survival probability of quantum walkers is compared with that of classical walkers. It is shown that the time dependence of survival probability of quantum walkers has a piecewise stretched exponential character depending on the density of traps in numerical and analytical observations. The crossover between the quantum analogs of the Rosenstock and Donsker-Varadhan behaviors is identified.

quant-ph↗

arXiv2009

Compensation temperature of 3d mixed ferro-ferrimagnetic ternary alloy

In this study, we have considered the three dimensional mixed ferro-ferrimagnetic ternary alloy model of the type AB$_{p}$C$_{1-p}$ where the A and X (X=B or C) ions are alternately connected and have different Ising spins S$^{A}$=3/2, S$^{B}$=1 and S$^{C}$=5/2, respectively. We have investigated the dependence of the critical and compensation temperatures of the model on concentration and interaction parameters by using MC simulation method. We have shown that the behavior of the critical temperature and the existence of compensation points strongly depend on interaction and concentration parameters. In particular, we have found that the critical temperature of the model is independent on concentration of different types of spins at a special interaction value and the model has one or two compensation temperature points in a certain range of values of the concentration of the different spins.

cond-mat.mtrl-sci↗

arXiv2009

Decoherence in Two-Dimensional Quantum Random Walks with Traps

Quantum random walk in a two-dimensional lattice with randomly distributed traps is investigated. Distributions of quantum walkers are evaluated dynamically for the cases of Hadamard, Fourier, and Grover coins, and quantum to classical transition is examined as a function of the density of the traps. It is shown that traps act as a serious and additional source of quantum decoherence. Furthermore, non-trivial temporal dependence of the standard deviation of the probability distribution of the walker is found when the trapping imperfections are introduced.

quant-ph↗

arXiv2008

Monte Carlo simulation for statistical mechanics model of ion channel cooperativity in cell membranes

Voltage-gated ion channels are key molecules for the generation and propagation of electrical signals in excitable cell membranes. The voltage-dependent switching of these channels between conducting and nonconducting states is a major factor in controlling the transmembrane voltage. In this study, a statistical mechanics model of these molecules has been discussed on the basis of a two-dimensional spin model. A new Hamiltonian and a new Monte Carlo simulation algorithm are introduced to simulate such a model. It was shown that the results well match the experimental data obtained from batrachotoxin-modified sodium channels in the squid giant axon using the cut-open axon technique.

physics.bio-ph↗

arXiv2008

Quantum information entropies of the eigenstates of the Morse potential

The position and momentum space information entropies for the Morse potential are numerically obtained for different strengths of the potential. It is found to satisfy the bound obtained by Beckner, Bialynicki-Birula, and Mycielski. Interesting features of the entropy densities are graphically demonstrated.

quant-ph↗

arXiv2006

Rotational Brownian motion on the sphere surface and rotational relaxation

The spatial components of the autocorrelation function of noninteracting dipoles are analytically obtained in terms of rotational Brownian motion on the surface of a unit sphere using multi-level jumping formalism based on Debye's rotational relaxation model, and the rotational relaxation functions are evaluated.

cond-mat.stat-mech↗

arXiv2006

Non-exponential relaxation in disordered complex systems

We have analytically obtained the non-exponential relaxation function for disordered complex systems applying the multi-level jumping formalism to the fluctuation quantity which makes diffusive motion stochastically in the disordered complex space. It is shown that the relaxation function of disordered complex systems decays obey to stretched exponential law.

cond-mat.stat-mech↗

arXiv2005

Time dependence of the survival probability of an opinion in a closed community

The time dependence of the survival probability of an opinion in a closed community has been investigated in accordance with social temperature by using the Kawasaki-exchange dynamics based on previous study in Ref. [1]. It is shown that the survival probability of opinion decays with stretched exponential law consistent with previous static model. However, the crossover regime in the decay of the survival probability has been observed in this dynamic model unlike previous model. The decay characteristics of both two regimes obey to stretched exponential.

physics.soc-ph↗

arXiv2005

Magnetic plateaus in the 1D antiferromagnetic spin-3/2 and spin-2 Ising chains with single-ion anisotropy

In this study, we have employed the classical transfer matrix technique to investigate the magnetization plateaus, phase diagrams and other thermodynamical properties of the one-dimensional antiferromagnetic spin-3/2 and spin-2 Ising chains with single-ion anisotropy in the presence of an external magnetic field at very low temperature. We have showed that single ion-anisotropy is one of the indispensable ingredients for an energy gap which leads to magnetic plateau mechanism in one-dimensional antiferromagnetic Ising spin chains. Other thermodynamical predictions seem to be provide this argument.

cond-mat.stat-mech↗

arXiv2005

Anomalous Rotational Relaxation: A Fractional Fokker-Planck Equation Approach

In this study we obtained analytically relaxation function in terms of rotational correlation functions based on Brownian motion for complex disordered systems in a stochastic framework. We found out that rotational relaxation function has a fractional form for complex disordered systems, which indicates relaxation has non-exponential character obeys to Kohlrausch-William-Watts law, following the Mittag-Leffler decay.

cond-mat.stat-mech↗

arXiv2005

Ground State Properties of one-dimensional Antiferromagnetic Spin-1 Chain with Single-ion Anisotropy

In this study, we have investigated ground state properties of one-dimensional antiferromagnetic spin-1 chain with single-ion anisotropy at very low temperatures using the Transfer Matrix method. Magnetic plateaus, phase diagram, specific heat, susceptibility of the spin chain have been evaluated numerically from the free energy. Results are in good agreement with the experimental data for the spin-1 compounds [Ni$_2$(Medpt)$_2$($μ$-ox)(H$_2$O)$_2$](ClO$_4$)$_2$2H$_2$O, [Ni$_{2}$(Medpt)$_{2}$($μ$-ox)($μ$-N$_{3}$)](ClO$_{4}$)0.5H$_{2}$O, Ni(C$_2$H$_8$N$_2$)Ni(CN)$_4$ and Ni(C$_{10}$H$_8$N$_2$)$_2$Ni(CN)$_4$.H$_2$O. However, spin-Peierls transition have not been observed in the temperature dependence of specific heat and magnetic susceptibility.

cond-mat.stat-mech↗

arXiv2004

The time evaluation of resistance probability of a closed community against to occupation in a Sznajd like model with synchronous updating: A numerical study

In the present paper, we have briefly reviewed Sznajd's sociophysics model and its variants, and also we have proposed a simple Sznajd like sociophysics model based on Ising spin system in order to explain the time evaluation of resistance probability of a closed community against to occupation. Using a numerical method, we have shown that time evaluation of resistance probability of community has a non-exponential character which decays as stretched exponential independent the number of soldiers in one dimensional model. Furthermore, it has been astonishingly found that our simple sociophysics model is belong to the same universality class with random walk process on the trapping space.

cond-mat.stat-mech↗

arXiv2002

A Simple Chaotic Neuron Model : Stochastic Behavior of Neural Networks

We have shortly reviewed the occurrence of the post-synaptic potentials between neurons, the relation between EEG and neuron dynamics, as well as methods of signal analysis. We supposed a simple stochastic model representing electrical activity of neuronal systems. The model is constructed using the Monte Carlo simulation technique. The results yielded EEG-like signals with their phase portraits in three-dimensional space. The Lyapunov exponent was positive, indicating a chaotic behavior. The correlation dimension of the EEG-like signals was found to be .92, which was smaller than those reported by others. It was concluded that this neuron model may provide valuable clues about the dynamic behavior of neural systems.

cond-mat.stat-mech↗