arXiv subjects

M. R. Hadizadeh

Publications and source records attributed to M. R. Hadizadeh.

At least 19 recordsLinked to original sources

arXiv2023

Relativistic Faddeev 3D Equations for Three-Body Bound States Without Two-Body $t-$Matrices

This paper explores a novel revision of the Faddeev equation for three-body (3B) bound states, as initially proposed in Ref. \cite{golak2013three}. This innovative approach, referred to as \tmatrixfree in this paper, directly incorporates two-body (2B) interactions and completely avoids the 2B transition matrices. We extend this formalism to relativistic 3B bound states using a three-dimensional (3D) approach without using partial wave decomposition. To validate the proposed formulation, we perform a numerical study using spin-independent Malfliet-Tjon and Yamaguchi interactions. Our results demonstrate that the relativistic \tmatrixfree Faddeev equation, which directly implements boosted interactions, accurately reproduces the 3B mass eigenvalues obtained from the conventional form of Faddeev equation, referred to as \tmatrixdependent in this paper, with boosted 2B $t-$matrices. Moreover, the proposed formulation provides a simpler alternative to the standard approach, avoiding the computational complexity of calculating boosted 2B $t-$matrices and leading to significant computational time savings.

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arXiv2023

Four-body bound states in momentum space: the Yakubovsky approach without two-body $t-$matrices

This study presents a solution to the Yakubovsky equations for four-body bound states in momentum space, bypassing the common use of two-body $t-$matrices. Typically, such solutions are dependent on the fully-off-shell two-body $t-$matrices, which are obtained from the Lippmann-Schwinger integral equation for two-body subsystem energies controlled by the second and third Jacobi momenta. Instead, we use a version of the Yakubovsky equations that doesn't require $t-$matrices, facilitating the direct use of two-body interactions. This approach streamlines the programming and reduces computational time. Numerically, we found that this direct approach to the Yakubovsky equations, using 2B interactions, produces four-body binding energy results consistent with those obtained from the conventional $t-$matrix dependent Yakubovsky equations, for both separable (Yamaguchi and Gaussian) and non-separable (Malfliet-Tjon) interactions.

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arXiv2023

Tunable properties of excitons in double monolayer semiconductor heterostructures

We studied the exciton properties in double layers of transition metal dichalcogenides (TMDs) with a dielectric spacer between the layers. We developed a method based on an expansion of Chebyshev polynomials to solve the Wannier equation for the exciton. Corrections to the quasiparticle bandgap due to the dielectric environment were also included via the exchange self-energy calculated within a continuum model. We systematically investigated hetero double-layer systems for TMDs with chemical compounds MX2, showing the dependence of the inter- and intralayer excitons binding energies as a function of the spacer width and the dielectric constant. Moreover, we discussed how the exciton energy and its wave function, which includes the effects of the changing bandgap, depend on the geometric system setup.

cond-mat.mes-hall↗

arXiv2023

Trion clustering structure and binding energy in 2D semiconductor materials: Faddeev equations approach

In this work, we develop the basic formalism to study trions in semiconductor layered materials using the Faddeev equations in momentum space for three different particles lying in two dimensions. We solve the trion Faddeev coupled integral equations for both short-range one-term separable Yamaguchi potential and Rytova-Keldysh (RK) interaction applied to the MoS$_2$ layer. We devise two distinct regularization methods to overcome the challenge posed by the repulsive electron-electron RK potential in the numerical solution of the Faddeev equations in momentum space. The first method regulates the repulsive interaction in the infrared region, while the second regulates it in the ultraviolet region. By extrapolating the trion energy to the situation without screening, the two methods gave consistent results for the MoS$_2$ layer with a trion binding energy of $-49.5(1)$~meV for the exciton energy of $-753.3$~meV. We analyzed the trion structure for the RK and Yamaguchi potentials in detail, showing their overall similarities and the dominant cluster structure, where the strongly bound exciton is weakly bound to an electron. We found that this property is manifested in the dominance of two of the Faddeev components over the one where the hole is a spectator of the interacting electron pair.

cond-mat.mes-hall↗

arXiv2021

Three-boson stability for boosted interactions towards the zero-range limit

We study the three-boson bound-state mass and wave functions for ground and excited states within the three-body relativistic framework with Kamada and Glöcke boosted potentials in the limit of a zero-range interaction. We adopt a nonrelativistic short-range separable potential, with Yamaguchi and Gaussian form factors, and drive them towards the zero-range limit by letting the form factors' momentum scales go to large values while keeping the two-body binding fixed. We show that the three-boson relativistic masses and wave functions are model-independent towards the zero-range limit, and the Thomas collapse is avoided, while the nonrelativistic limit kept the Efimov effect. Furthermore, the stability in the zero-range limit is a result of the reduction of boosted potential with the increase of the virtual pair center of mass momentum within the three-boson system. Finally, we compare the present results with Light-Front and Euclidean calculations.

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arXiv2021

Relativistic nucleon-nucleon potentials in a spin-dependent three-dimensional approach

The matrix elements of relativistic nucleon-nucleon $(NN)$ potentials are calculated directly from the nonrelativistic potentials as a function of relative $NN$ momentum vectors, without using a partial wave decomposition. To this aim, the quadratic operator relation between the relativistic and nonrelativistic $NN$ potentials is formulated in momentum-helicity basis states. It leads to a single integral equation for the two-nucleon $(2N)$ spin-singlet state and four coupled integral equations for two-nucleon spin-triplet states, which are solved by an iterative method. Our numerical analysis indicates that the relativistic $NN$ potential obtained using CD-Bonn potential reproduces the deuteron binding energy and neutron-proton elastic scattering differential and total cross-sections with high accuracy.

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arXiv2020

A Novel Regularization Scheme for Nucleon-Nucleon Lattice Simulations with Effective Field Theory

We propose a new regularization scheme to study the bound state of two-nucleon systems in Lattice Effective Field Theory. Inspired by continuum EFT calculation, we study an exponential regulator acting on the leading-order (LO) and next-to-leading order (NLO) interactions, consisting of local contact terms. By fitting the low-energy coefficients (LECs) to deuteron binding energy and the asymptotic normalization coefficient (ANC) on a lattice simulation, we extract the effective range expansion (ERE) parameters in the $^3S_1$ channel to order $p^2$. We explore the impact of different powers of the regulator on the extracted ERE parameters for the lattice spacing $a=1.97$ fm. Moreover, we investigate how the implementation of the regularization scheme improves the predicted ERE parameters on the lattice spacing in the range of $1.4 \le a \le 2.6$ fm. Our numerical analysis indicates that for lattice spacing greater than $2$ fm, the predicted observables are very close to the experimental data.

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arXiv2020

A three-dimensional momentum-space calculation of three-body bound state in a relativistic Faddeev scheme

In this paper, we study the relativistic effects in a three-body bound state. For this purpose, the relativistic form of the Faddeev equations is solved in momentum space as a function of the Jacobi momentum vectors without using a partial wave decomposition. The inputs for the three-dimensional Faddeev integral equation are the off-shell boost two-body $t-$matrices, which are calculated directly from the boost two-body interactions by solving the Lippmann-Schwinger equation. The matrix elements of the boost interactions are obtained from the nonrelativistic interactions by solving a nonlinear integral equation using an iterative scheme. The relativistic effects on three-body binding energy are calculated for the Malfliet-Tjon potential. Our calculations show that the relativistic effects lead to a roughly 2\% reduction in the three-body binding energy. The contribution of different Faddeev components in the normalization of the relativistic three-body wave function is studied in detail. The accuracy of our numerical solutions is tested by calculation of the expectation value of the three-body mass operator, which shows an excellent agreement with the relativistic energy eigenvalue.

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arXiv2019

Momentum space calculations of the binding energies of argon dimer

The binding energies of argon dimer are calculated by solving the homogeneous Lippmann-Schwinger integral equation in momentum space. Our numerical analysis using two models of argon-argon interaction developed by Patkowski {\it et al.} confirms not only the eight argon dimer vibrational levels of the ground state of argon dimer (i.e. for $j=0$) predicted by other groups but also provides a very precise means for determining the binding energy of the ninth state which its value is a matter of discussion. Our calculations have been also extended to states with higher rotational quantum number $j$ and we have calculated the energy of all 174 bound states for both potential models. Our numerical results for vibrational levels of the ground state of argon dimer are in excellent agreement with other theoretical calculations and available experimental data.

physics.chem-ph↗

arXiv2017

Probing the Efimov discrete scaling in atom-molecule collision

The discrete Efimov scaling behavior, well-known in the low-energy spectrum of three-body bound systems for large scattering lengths (unitary limit), is identified in the energy dependence of atom-molecule elastic cross-section in mass imbalanced systems. That happens in the collision of a heavy atom with mass $m_H$ with a weakly-bound dimer formed by the heavy atom and a lighter one with mass $m_L \ll m_H$. Approaching the heavy-light unitary limit the $s-$wave elastic cross-section $σ$ will present a sequence of zeros/minima at collision energies following closely the Efimov geometrical law. Our results open a new perspective to detect the discrete scaling behavior from low-energy scattering data, which is timely in view of the ongoing experiments with ultra-cold binary mixtures having strong mass asymmetries, such as Lithium and Caesium or Lithium and Ytterbium.

physics.atom-ph↗

arXiv2017

Comment on "Six-body bound system calculations in the case of effective $α-$core structure" [Eur. Phys. J. Plus (2016) 131: 240]

The authors argue that the calculated $^6$He binding energies by the solution of the coupled Yakubovsky integral equation in a partial wave decomposition reported by E. Ahmadi Pouya and A. A. Rajabi [Eur. Phys. J. Plus (2016) 131: 240] are incorrect. The formalism of the paper has serious mistakes and the numerical results are not reproducible and cannot be validated.

nucl-th↗

arXiv2017

Comment on "Three-dimensional study of the six-body bound-state for the case of effective three-body configuration model" [Int. J. Mod. Phys. E 25, 9 (2016) 1650072]

The authors argue that the calculated $^6$He binding energies by the solution of the coupled Faddeev-Yakubovsky integral equation in a Three-dimensional scheme reported by E. Ahmadi Pouya and A. A. Rajabi [Int. J. Mod. Phys. E 25, 9 (2016) 1650072] are incorrect. The formalism of the paper has serious mistakes and the numerical results are quite misleading because such a calculation even with small grids for Jacobi momenta and the angle variables leads to a huge memory of 37.8 PB (petabyte) which cannot even be achieved on present supercomputers.

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arXiv2017

Universality in the neutron$-^{19}$C scattering using finite range separable interactions

We report a study on the low-energy properties of the elastic $s-$wave scattering of a neutron ($n$) in the carbon isotope $^{19}$C near the critical condition for the occurrence of an excited Efimov state in the three-body $n-n-^{18}$C system. For the separation energy of the two halo neutrons in $^{20}$C we use the available experimental data. We also investigate to which extent the universal scaling laws, strictly valid in the zero-range limit, will survive when using finite-range interactions. By allowing to vary the $n-^{18}$C binding energy, a scaling behavior for the real and imaginary parts of the $s-$wave phase-shift $δ_0$ is verified, emerging some universal characteristics given by the pole-position of $k\cot(δ_0^R)$ and effective-range parameters.

nucl-th↗

arXiv2017

Calculation of Relativistic Nucleon-Nucleon Potentials in Three-Dimensions

In this paper, we have applied a three-dimensional approach for calculation of the relativistic nucleon-nucleon potential. The quadratic operator relation between the non-relativistic and the relativistic nucleon-nucleon interactions is formulated as a function of relative two-nucleon momentum vectors, which leads to a three-dimensional integral equation. The integral equation is solved by the iteration method, and the matrix elements of the relativistic potential are calculated from non-relativistic ones. Spin-independent Malfliet-Tjon potential is employed in the numerical calculations, and the numerical tests indicate that the two-nucleon observables calculated by the relativistic potential are preserved with high accuracy.

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arXiv2016

Neutron$-^{19}$C scattering: emergence of universal properties in a finite range potential

The low-energy properties of the elastic $s-$wave scattering for the $n-^{19}$C are studied near the critical condition for the occurrence of an excited Efimov state in $n-n-^{18}$C. It is established to which extent the universal scaling laws, strictly valid in the zero-range limit, survive when finite range potentials are considered. By fixing the two-neutrons separation energy in $^{20}$C with available experimental data, it is studied the scaling of the real ($δ_0^R$) and imaginary parts of the $s-$wave phase-shift with the variation of the $n-^{18}$C binding energy. We obtain some universal characteristics given by the pole-position of $k\cot(δ_0^R)$ and effective-range parameters. By increasing the $n-^{18}$C binding energy, it was verified that the excited state of $^{20}$C goes to a virtual state, resembling the neutron-deuteron behavior in the triton. It is confirmed that the analytical structure of the unitary cut is not affected by the range of the potential or mass asymmetry of the three-body system.

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arXiv2016

R-Matrix Calculations for Few-Quark Bound States

The R--matrix method is implemented to study the heavy charm and bottom diquark, triquark, tetraquark and pentaquarks in configuration space, as the bound states of quark--antiquark, diquark--quark, diquark--antidiquark and diquark--antitriquark systems, respectively. The mass spectrum and the size of these systems are calculated for different partial wave channels. The calculated masses are compared with recent theoretical results obtained by other methods in momentum and configuration spaces and also by available experimental data.

hep-ph↗

arXiv2015

Heavy Tetraquarks in the Diquark-Antidiquark Picture

The homogeneous Lippmann-Schwinger integral equation is solved in momentum space to calculate the masses of heavy tetraquarks with hidden charm and bottom. The tetraquark bound states are studied in the diquark-antidiquark picture as a two-body problem. A regularized form of the diquark-antidiquark potential is used to overcome the singularity of the confining potential at large distances or small momenta. Our numerical results indicate that the relativistic effect leads to a small reduction in the mass of heavy tetraquarks, which is less than $2\,\%$ for charm and less than $0.2\,\%$ for bottom tetraquarks. The calculated masses of heavy tetraquarks for $1s$, $1p$, $2s$, $1d$ and $2p$ states are in good agreement with other theoretical calculations and experimental data. Our numerical analysis predict the masses of heavy tetraquarks for $3s$, $2d$ and $3p$ states for the first time, and we are not aware of any other theoretical results or experimental data for these states.

hep-ph↗

arXiv2015

Scaling functions of two-neutron separation energies of $^{20}C$ with finite range potentials

The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus $^{20}C$.

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