مجله پژوهش فیزیک ایران
سال بیست و دوم شماره 4 (زمستان 1401)

We study a model for production of stable micro black holes based on investigation of the thermodynamics of micro black holes and the LHC test. That showed how this production can be obtained by a thermodynamic process of stability. The general second law of black hole thermodynamics plays an important role here and, through Hawking radiation and fusion reactions entropy formulas a valid total entropic is obtained. Therefore, we reach an energy of stability by quantum perturbation expansion over this total entropic formula that is illustrated in detail in this paper. Based on this study, the producing of stable particles (in terms of our investigation, micro-black holes) at the LHC might yielded an interesting result that it is worth a try, which could have different results.

In this study, in order to reduce the background spectrum in Doppler broadening spectroscopy and, to use information about the tail of spectrum, which is mainly due to the annihilation of positrons by core electrons, a new setup was introduced and the results has been analyzed by the relativity formula. The results show that after the positron enters the sample and is annihilated by the valance and core electrons of the  lattice structure, in addition to the two main gamma rays, unwanted gammas caused by the Compton phenomenon and their annihilation outside the sample. In a Doppler broadening spectroscopy, the electrons' energy band information disappears from the researchers' view due to the overlap of the main spectrum with the background spectrum. This extra and unwanted background spectrum wastes a lot of time and energy in studying the structure of materials with the help of this spectrometer. To solve this problem, our research team has developed a new laboratory layout plan after detailed studies, which in addition to reducing the count of unwanted gammas, has also significantly reduced the recording time of the spectrum. The results of this new spectroscopic method compared to the traditional method show a significant reduction in the recording of unwanted gammas and, as a result, a significant increase in the detection of 99% of gammas due to the annihilation of positrons by core electrons.

Recently, the ΛΛ potential at nearly physical quark masses has been calculated in the lattice QCD simulations by the HAL QCD Collaboration which are the most consistent potential with the experimental data. In this study making use of this ΛΛ interaction the binding energy and the radius matter for the ground state of hypernucleus (_ΛΛ^6)He is calculated via solving the coupled Faddeev equations. Here, for the Λα interaction; three different and common types of interactions, the Isle-type potential, the single Gaussian potential and the Maeda-Schmidt potential are examined. Numerical analyzes for (_ΛΛ^6)He using three ΛΛ interaction models and three models of phenomenological Λα interaction lead to the values of ground state energy between 7.197 and 8.408 MeV, and the value of the radius of matter in the range of 1.731 to 1.954 fm. Numerical results show that the minimum value of ground state binding energy, which is closest to the experimental value, occurs when one uses the HAL QCD ΛΛ potential at lattice time t⁄a=12 and the MS phenomenological type Λα potential. Also, the geometrical properties of (_ΛΛ^6)He system are investigated.

Copper is one of the very harmful metals for human’s life, may lead to headaches, depression and learning disabilities, which is a very vital issue. Moreover, this metal is not biodegradable and remains in nature for a long time. Metal oxide nanoparticles with high surface adsorption can be used as a suitable option for copper removal from factory effluents. In this paper, aluminum oxide nanoparticles are proposed, synthesized and investigated as nanoparticles with high adsorption. Also, the synthesis is based on two different precursors (aluminum chloride and aluminum nitrate) and the effect of precursor is investigated on the structural and optical properties of alumina nanoparticles. Studies show that alumina nanoparticles are formed with both precursors, and they are amorphous. However, the choice of precursor has a significant effect on the size of the nanoparticles and the optical properties of these alumina nanoparticles. In addition, the study of the effect of precursor selection on the copper cation removal at pH = 5.7 shows that alumina nanoparticles synthesized with aluminum nitrate have better copper removal efficiency than the sample synthesized with aluminum chloride precursor and the removal of copper contaminants (20 ppm) with this alumina nanoparticles reaches 91% in 180 minutes, which indicates the excellent performance of synthesized nanoparticles in copper removal.

Quantum state discrimination between optical coherent superposition states is considered. The Helstrom bound for imperfect detection is evaluated. Under a physically realistic model of photodetection, we study several techniques for discriminating between optical coherent superposition states. We investigate quantum error probabilities for the Kennedy receiver, the Dolinar receiver and the unitary rotation scheme proposed by Sasaki and Hirota for sub-unity detector efficiency. Also, we study the feedback strategy employed by the Dolinar receiver to achieve the Helstrom bound for sub-unity detection efficiency.

Solar collectors are necessary optical devices for converting solar irradiation into heat. Their optical characteristics are necessary prior to construction. The construction error and the slope error of the surface mirror facet of a parabolic solar collector have been measured by the optical scanning method. The material of the mirror layer is reinforced fiberglass, which is designed and made by molding method and its approximate area is 0.8 square meters. In the optical scanning method, a structured light mechanism and off-axis imaging are used. In addition to the location of each point, the depth of that point is measured and a cloud is obtained from the surface points of the part. By fitting a parabolic procedure with a focal length of 3,000 millimeters (specified in the design file of the part), the vertical deviation of the measuring points (actual) on the part with the design file points (nominal) was determined. The Root Mean Square geometric difference from point to point of the constructed part compared to the designed part was approximately 1.2 mm. The effect of surface slope error was calculated in terms of the normal vector angular deviation of each point from the ideal surface and the amount of ±15.7 mrad angular deviations was calculated for this procedure. The cloud of points measured by the optical scan was inserted into the Zemax software environment and the focal intensity pattern obtained from this fiberglass procedure was simulated by the Monte Carlo method. Next, a thin layer of the mirror was stuck on the substrate. The temperature profile of the concentrated light on the focal area was measured on an iron plate receiver with a thermal camera and the maximum surface temperature of 140 ° C was recorded.

In this paper, flat potentials (μ│x / a│N) are numerically investigated by pseudo-spectral method. The Schrodinger equation of this type of potential has become an eigen system using the pseudo-spectral method. The eigen system is then diagonalized by the Jacobi method. Energy eigen values for different Ns have been compared with similar articles. The limit behavior of this potential for the states N = 2 and N → ∞ is related to the harmonic oscillator and the particle in the box with length 2a, respectively. For each N, a function is proposed for energy eigen values in terms of the quantum number n. By using of data fitting, the correctness of the proposed equation is checked.

In this paper, we study the magnonic transport properties of an antiferromagnetic chain that is connected to two semi-infinite ferromagnetic leads by using the transfer matrix approach. The antiferromagnetic chain is assumed to be located in a magnonic dissipative environment when an external magnetic field is applied to it. We improved the model in a way that the numerical calculations are rapidly done. In the following, we perform the numerical calculations to obtain the magnonic transmission coefficient and density of states of a multi-atomic antiferromagnetic chain as an illustrative example and we present its results in detail, in the presence of magnetic field and magnonic dissipative forces. Controlling of the resonance region width and the number of peaks in magnonic conductance spectra by variation of the magnetic field amount, the length of the chain, and the magnetic parameters of the system are discussed.

In this paper, the two Higgs doublet model (2HDM) is investigated for simultaneous observation of the signals of the neutral Higgs particles. The goal of this work is to introduce model types which result in observable signals for these particles at future lepton colliders. Then for every selected type, the parameter space of the model is investigated and the mass regions of the neutral Higgs bosons which are suitable for finding their signals are identified. Introducing several example values for the masses of these particles, events of electron-positron collisions with center of mass energy of 1000 GeV are generated, and taking into account the effects of a typical detector, they are analyzed and the Higgs particles masses are reconstructed. Plots obtained in this analysis are one of the richest possible plots for the Higgs particles signals and provide information about the Z particle mass, the light Higgs particle with the mass of 125 GeV and heavy neutral Higgs particles (H, A) at the same time. Finally, estimations about the needed amount of data for the observation of the signal of the neutral Higgs particles are provided.

In a holographic compressible quantum matter, we calculate the sound mode using holography. For this purpose, we consider a structure of D3-D7 branes that corresponds to this holographic compressible quantum matter. In this system, the sound mode is called the zero sound mode. In Gauss-Bonnet gravitational field geometry, we calculate the corrections entered at zero sound and show that the attenuation rate decreases.

In this work, plasma has been used as a simple, very fast, low energy and efficient method for modification of the zinc oxide nanopowder to improve its photocatalytic activity. Zinc oxide is one of the effective photocatalysts in degradation of the organic contaminants, e.g. dyes. The purpose of the zinc oxide photocatalyst modification is to reduce the band gap and thus to increase its photocatalytic activity in the visible light range. To achieve nitrogen-doped zinc oxide nanoparticles (N-Doped ZnO), the zinc oxide nanopowder was suspended in melamine solution, as nitrogen precursor, and then treated with a non-thermal atmospheric pressure plasma. Different concentrations of melamine and different times of plasma exposure were considered for optimizing the nitrogen-doped zinc oxide structure. The photocatalyst properties of the pure zinc oxide and optimized nitrogen-doped zinc oxide samples were investigated by XRD, FESEM, EDX, BET, DRS and PL analyses. The photocatalytic activity of the pure zinc oxide nanopowder and plasma-treated samples were performed in the photocatalytic degradation of methylene blue dye contaminant. The degradation efficiency of methylene blue by the pure zinc oxide was 71.7%. By applying plasma to the zinc oxide nanopowder for 5 minutes with a concentration of 500 mg/L of melamine solution, the degradation efficiency was enhanced to 90%. According to the results, it can be seen that the plasma treatment has succeeded in the nitrogen doping process to the zinc oxide structure and improved its photocatalytic activity.

In this study, a new method for measuring the velocity of plasma bullets, based on receiving and detecting the electrical signal of the bullets using an array of cascading antennas in an argon plasma jet with a tip-ring structure is presented. In this structure, the tip electrode plays the role of igniter of plasma generation and the ring electrode plays the role of controlling the plasma jet. To study the variations in the plasma jet, the ring electrode was located at different distances from the tip electrode and the variations in the velocity of the bullets were measured. The experiments showed that if the two electrodes were 1.5 cm apart, at a distance of 15 cm from the plasma formation site, the velocity of the bullets would be about 140 km/s. If the two electrodes are 3.25 cm apart, the bullets will have a speed of about 120 km/s, and if the two electrodes are 5 cm apart, the bullets will have a speed of about 100 km/s. Examination of the results showed that by increasing the distance between the two electrodes, the velocity of plasma bullets also decreases significantly. The results also showed that by moving away from the plasma formation site in the jet tube, the average velocity of plasma bullets increases. For example, at a distance of 21 cm from it, the average speed of plasma bullets in all three configurations will be about 120 km/s. Finally, by varying the electrical power, we concluded that as the electrical power increases, the speed of the bullets increases. According to the obtained results, by doubling the applied power, it was observed that at a distance of 15 cm from the place of plasma formation, the velocity of the bullets will be about 40 km/s at lower power and about 90 km/s at higher power; These results are obtained if the distance between the two electrodes is 3.25 cm and the initial electrical power is 20 Watts.

We consider two nonlinear electrical circuits consisting of two nonlinear capacitors that are coupled to each other through linear inductors (mutual induction) under the influence of time-dependent external fields. By excitation of two non-linear chaos  electrical circuits (chaos oscillators) by each other, the Lyapunov indexes were extracted numerically and the synchronization of two electrical circuits without chaos connection was observed. The dependence of  the Lyapunov exponent on the numerical value of the coupling coefficient (mutual induction m) has been studied and the critical value of this coefficient has been determined. Also, the effect of this coupling coefficient of two nonlinear electrical circuits (two Duffing oscillators) coupled without connection has been investigated in order to observe different dynamic states. Diagrams of charge and current changes in terms of time for the numerical value of critical mutual induction have been studied and the synchronization of the two circuits is shown.

One of the most fascinating features of cosmology is the study of large structures that can reveal the properties of particles with the smallest known cross sections (neutrinos). In fact, in the early universe, after photons, neutrinos play an important role in the formation of structures. The large number of neutrinos, combined with their non-zero mass, leads to today's energy density at least 25 times larger than CMB photons. This high density of free-flowing particles leads to changes in the large-scale structure (LSS) that can be recorded in large galaxy studies or dark current measurements. The purpose of this paper is to determine the direction of bulk flow and other cosmic parameters using the quintessence model. In this paper, we also estimate the mass of neutrinos using neutrino coupling and the scalar field of quintessence. The data where used in this article is the Pantheon Catalog, a total of 1048 Type Ia supernovae. The direction of the bulk flow is slightly different on scales smaller than 0.1, and the higher the scale of the local world, the greater the difference in the direction of the bulk current.

In light of the recently observed electronic recoil in the XENON1T experiment, we revisit the phenomenology of vector dark matter in leptophilic extension of the standard model while, new scalar, vector and spinor fields play the role of mediators. The viable parameter spaces are considered to discuss the possibility of light vector dark matter with mass 2.3 keV and sufficient dark matter relic density. We also study the constraints of the anomalous magnetic moment of the muon, baryon nucleon synthesis and indirect detection experiments on the parameter space of the models.

The total kinetic energy (TKE) of fission fragments for some heavy actinides fission is investigated and calculated using the scission point model. First, the deformation parameters of fission fragments are obtained by fitting the calculated results to the available experimental data. Then, the deformation parameters of fission fragments and the behavior of TKE distribution are investigated for heavy actinides fission. This indicates that the Usang model can better explaine the TKE distribution for actinides heavier than californium than the Unik model. Also, the TKE value can be approximated by the sum of the Coulomb and nuclear energies of the fission fragments for light actinides, but this approximation is not correct for very heavy actinides such as fermium. Because the values of pre-scission kinetic energy are very different from the nuclear potential energy in the heavy actinides region. Finally, the distributions of TKE for spontaneous fission of 242Am, 244Am, 244Cm, 246Cm, 248Cm, 250Cf,  and  254Cf are evaluated using the scission point model.

In this study the variation of dissolved ozone in deionized water was investigated using the real-time measurement technique. The ozone gas was generated by a homemade coaxial dielectric barrier discharge and injected into the bottom of the water column via a bubbler. The values of ozone concentration were measured by the UV absorption spectra obtained by two quartz windows mounted inside the water column. The results showed a fast increasing of dissolved ozone at the first 3 min and then, the concentration reaches to an approximately constant value which depends on the water temperature and gas phase ozone concentration. The highest concentration of dissolved ozone was obtained about 3.5 ppm at the lowest temperature (2ºC) when the input gas contains 2500 ppm of ozone. The measurements were also continued after turning off the bubbler and decreasing of dissolved ozone were monitored. An approximate exponential decay of ozone was observed whose gradient  did not show any meaningful dependency on temperature and treatment time of water.

With the increasing use of particle accelerators in various fields, the construction of accelerators has developed. In these accelerators, measurement instruments that measure important and versatile quantities are very important. Due to the role of electric potential in particle acceleration, accurate measurement of electric potential at any time in accelerators is essential. In this research, design, fabrication and testing of a non-destructive electric potential measuring device called Generating Voltmeter (GVM) has been done. This instrument uses the principle of capacitance changes to measure voltage. Also, the effect of various parameters such as the number of rotor blades, stator thickness and diameter on the instrument performance  has been investigated. Finally, a suitable GVM has been selected for use in the dynamitron electrostatic accelerator at the Nuclear Science and Technology Research Institute.

Consider an open quantum system S, interacting with its environment E, and also an ancillary Hilbert space R. The reduced dynamics of the system S  is given by a completely positive map, if the set S={ρSE}  , of possible initial states of the system-environment, can be written as a steered set from a tripartite Markov state ƮRSE. In this paper, we call such steered states  as Markovian states ρSE, and study a physical case, in which the reduced dynamics of the system can be completely positive, even when the initial states of the system-environment ρSE are non-Markovian.

Based on density functional theory (DFT) at the B3LYP level, we investigated the interaction of DNA nucleobases with carbon nano-rings in armchair and zigzag shapes. Van der Waals correction was applied to describe the long range term of bipolar interaction. Results indicate that a net electric charge was not transferred between the DNA bases and the carbon nano-rings. This indicates the interaction is of physical type. Outcomes show the following order for the strength of the interaction between the carbon nano-ring (9,9) and the four DNA nucleobases: guanine > adenine > cytosine > thymine. The corresponding order for the zigzag carbon nano-ring (15.0) is adenine ≈ guanine > cytosine > thymine, suggesting carbon nano-ring (9,9) may have a potential to specify the sequencing of DNA.

In this paper, the electrical characteristics of a nanoscale double gate metal source drain transistor is thoroughly investigated. Since reduction of the channel thickness results in the variation of energy level in sub-bands and increment of band gap energy, the bandstructure of the device is calculated via employing sp3d5s* tight binding formalism in 2D Hamiltonian with one atomic layer precision. Next, the effective mass of carriers is derived from the related bandstructure as a function of different channel thicknesses. Based on the obtained results, the carrier effective mass considerably increases in comparison with the related bulk values as the channel thickness scales down. Following that, the drive current of the device is calculated via Green’s function formalism. Furthermore, a statistical analysis was conducted to calculate the sensitivity of the main electrical measures with respect to the variation of critical physical and structural design parameters. By scaling down the channel thickness and increment of the effective Schottky barrier height, a potential well is created in the channel along the source and drain, which makes resonant tunneling occur at low temperatures and as a consequence, results in the occurrence of negative differential resistance in the transfer characteristics of the device. The impact of critical design parameters on the resonant tunneling phenomena in the proposed device is thoroughly investigated.

We studied the identical-nematic (I-N) phase transition of hard cylinders confined between two hard walls when using Onsager and Parsons-Lee theories and the Zwanzig approximation. The obtained results show the difference in predicting the I-N phase transition of the systems studied by these two theories. The results of Onsager theory are consistent with the previous paper, but the results of Parsons-Lee predict a completely different behavior. Compared to the previous results, our results occur at higher densities, which is due to the use of the Zwanzig approximation. Since Onsager model is accurate for highly elongated particles, we expect the two theories to provide a more accurate and similar answer for elongated particles, which was met in the investigations. Therefore, it seems that Onsager theory provides more appropriate result in the studied cases. It should be noted that what can give a more accurate judgment about these results is the simulation of a similar system of limited cylinders in a quasi-two-dimensional space. According to the literature review, the Parsons-Lee theory has given very good results for three dimensional systems, where two or more layers can form in the pores, however, it does not work properly for a monolayer of confined hard cylinders. Therefore, for such systems, it is necessary to modify the Parsons-Lee pre-factor to provide reliable results. This pre-factor has been calculated for three-dimensional systems in which the geometrical shape of particles is mapped to spheres of the same volume, not for two-dimensional systems. Because the image of a cylinder in two dimensions is a rectangle, and hard rectangles must map to hard disks, it is necessary to formulate a pre-factor and the Carnahan-Starling equation for disks in two-dimensional and quasi-two-dimensional systems

In this paper, we used the Particle in Cell (PIC) method to study a plasma in the Hall Effect thruster in order to optimize the effective parameters on the electron mobility and anomalous electrons drift. In the Hall Effect thrusters magnetic and electrical fields which are perpendicular to each other are used to confine the plasma and create propulsive force on the satellites and spacecrafts. The presence of a magnetic field perpendicular to the electric field causes the electrons to move in an azimuthal direction and in ideal situation it is expected that there is a net electron azimuthal current but we realize in the experimental tests that the electrons have anomalous drift. This anomalous drift causes a weak confinement of elections near the outlet of the thruster and increases the losses of electrons that it is a consequence of corrosion of the wall of the thruster which is made up of the dielectric, and it decreases the efficiency. Two major mechanisms have been proposed to control this electron current, the first is involving electron-wall collisions and the second one is involving plasma oscillations such as E×B drift instability. In this paper, these two subjects are investigated and the effective parameters on electron mobility are optimized. The simulation shows that the ideal value for a magnetic field to confine electrons is about 250 to 300 Gauss, and the reasonable value for accelerating electrons is more than 300 Volts. It is also shown that the optimal density of plasma and neutral gas is 2×1017 m-3 and 1×1020 m-3 respectively.

In this study, the specific activity of natural and artificial radioactive elements was measured for 50 sediment samples collected from throughout Miankaleh wetland in northern Iran on the southeastern side of the Caspian Sea using a High-Purity Germanium detector. Also, radiological parameters and hazard indicators due to environmental gamma radiation caused by these nuclei were calculated and a distribution map of Radium equivalent activity and absorbed Dose for the whole Miankaleh wetland was drawn using GIS software. The mean specific activity of 226Ra, 232Th, 40K and 137Cs respectively were 16.06±1.65, 21.19±1.46, 312.37±8.17 and 4.81±0.27 Bqkg-1 that for natural radioactive nuclei are less than the global average. The highest concentration of 226Ra is related to the sediments of the estuary of the Galougah River. The results show rapid deposition of 232Th immediately after entering the lagoon. The highest concentrations of 40K and 137Cs were observed in the mouth of the Gaz River and the calm part in the central area of the wetland, respectively. The mean values of Raeq and D respectively were 70.42±4.37 Bqkg-1 and 32.73 nGyh-1, which are less than the global average. The distribution map of Raeq and D shows the high amount of these two parameters in the sediments of the southern and eastern parts of the wetland, which is due to the entry of radionuclei by the water flow of rivers of this wetland basin. In general, the amount of radioactivity expressed in terms of radium equivalent in the wetland is higher near the mouth of rivers with higher water flow. The average value for AEDEout, ELCR, AGDE, Iγ and Hex in this wetland is less than the allowable value and, in general, the results of this study show that the amount of radiation due to the radionuclei in Miankaleh wetland does not pose radiological hazards to the health of the inhabitants of this area.

Since the establishment of the quantum mechanics, researchers in physics have been studying superposition states and especially proposing setups for generating macroscopic objects in a quantum superposition state. Such states are important and of interest both from a foundational perspective and for their applications in the emerging quantum technologies. Here, we propose a circuit quantum electrodynamical setup and an adiabatic scheme for preparing a macroscopic and massive object in a quantum superposition state. The scheme is based on establishing a spatial double-well potential for a macroscopic object and preparing it in the ground state of the potential via an adiabatic transition. The resulting state is a spatial superposition state where the object assumes a superposition of bulked to two opposite directions, e.g. right and left. By numerical solving of the quantum optical master equation and including the environmental effects, we show that the target cat state is achievable with a high fidelity provided the process satisfies the adiabaticity conditions.