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Silviu Olariu

Publications and source records attributed to Silviu Olariu.

At least 19 recordsLinked to original sources

Gamma Resonances near Threshold for the Production of Thermal Photoneutrons

We have determined the positions of the (gamma,n) resonances and upper limits for the integrated cross sections for the (gamma,n) reactions, using data for the inverse process (n,gamma). With the aid of these data we have estimated the number of low-energy neutrons which can be generated by the irradiation of a target with a gamma-ray beam. Among the reactions producing thermal neutrons via (gamma,n) reaction we mention 185Re(gamma,n)184Re with an upper limit of the integrated cross section of 2.4 b-eV, and 178Hf(gamma,n)177Hf with an upper limit of the integrated cross section of 0.9 b-eV.

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Complex Numbers in n Dimensions

This monograph presents a detailed analysis of hypercomplex numbers in 2, 3 and 4 dimensions, then presents the properties of hypercomplex numbers in 5 and 6 dimensions. It continues with a detailed analysis of hypercomplex numbers in n dimensions, and two distinct systems of commutative complex numbers are described, of polar and planar types. Exponential forms of n-complex numbers are given in each case, which depend on geometric variables. Azimuthal angles, which are cyclic variables, appear in these forms at the exponent, and this leads to the concept of residue for path integrals of n-complex functions. The exponential function of an n-complex number is expanded in terms of functions called in this paper cosexponential functions, which are generalizations to n dimensions of the circular and hyperbolic sine and cosine functions. The factorization of n-complex polynomials is discussed. The essence of this monograph is the interplay between the algebraic, the geometric and the analytic facets of the relations.

math.CV

Hyperbolic complex numbers in two dimensions

A system of commutative hyperbolic complex numbers in 2 dimensions is studied in this paper. Exponential and trigonometric forms are obtained for these hyperbolic twocomplex numbers. Expressions are given for the elementary functions of hyperbolic twocomplex variable. The functions of a hyperbolic twocomplex variable which are defined by power series are analytic. Relations of equality exist between partial derivatives of the real components a function of a hyperbolic twocomplex variable. The integral of a twocomplex function between two points is independent of the path connecting the points. A hyperbolic twocomplex polynomial can be written as a product of linear or quadratic factors, although the factorization may not be unique.

math.CV

Complex numbers in three dimensions

A system of commutative hypercomplex numbers of the form w=x+hy+kz are introduced in 3 dimensions, the variables x, y and z being real numbers. The multiplication rules for the complex units h, k are h^2=k, k^2=h, hk=1. The operations of addition and multiplication of the tricomplex numbers introduced in this paper have a simple geometric interpretation based on the modulus d, amplitude ρ, polar angle θand azimuthal angle ϕ. Exponential and trigonometric forms are obtained for the tricomplex numbers, depending on the variables d, ρ, θand ϕ. The tricomplex functions defined by series of powers are analytic, and the partial derivatives of the components of the tricomplex functions are closely related. The integrals of tricomplex functions are independent of path in regions where the functions are regular. The fact that the exponential form of the tricomplex numbers contains the cyclic variable ϕleads to the concepts of pole and residue for integrals of tricomplex functions on closed paths. The polynomials of tricomplex variables can be written as products of linear or quadratic factors.

math.CV

Commutative complex numbers in four dimensions

Commutative complex numbers of the form u=x+αy+βz+γt in 4 dimensions are studied, the variables x, y, z and t being real numbers. Four distinct types of multiplication rules for the complex bases α, βand γare investigated, which correspond to hypercomplex entities called in this paper circular fourcomplex numbers, hyperbolic fourcomplex numbers, planar fourcomplex numbers, and polar fourcompex numbers. Exponential and trigonometric forms for the fourcomplex numbers are given in all these cases. Expressions are given for the elementary functions of the fourcomplex variables mentioned above. Relations of equality exist between the partial derivatives of the real components of the functions of fourcomplex variables. The integral of a fourcomplex function between two points is independent of the path connecting the points. The concepts of poles and residues can be introduced for the circular, planar, and polar fourcomplex numbers, for which the exponential forms depend on cyclic variables. A hypercomplex polynomial can be written as a product of linear factors for circular and planar fourcomplex numbers, and as a product of linear or quadratic factors for the hyperbolic and polar fourcomplex numbers.

math.CV

Complex numbers in 5 dimensions

A system of commutative complex numbers in 5 dimensions of the form u=x_0+h_1x_1+h_2x_2+h_3x_3+h_4x_4 is described in this paper, the variables x_0, x_1, x_2, x_3, x_4 being real numbers. The operations of addition and multiplication of the 5-complex numbers introduced in this work have a geometric interpretation based on the the modulus d, the amplitude ρ, the polar angle θ_+, the planar angle ψ_1, and the azimuthal angles ϕ_1,ϕ_2. The exponential function of a 5-complex number can be expanded in terms of polar 5-dimensional cosexponential functions g_{5k}(y), k=0,1,2,3,4, and the expressions of these functions are obtained from the properties of the exponential function of a 5-complex variable. Exponential and trigonometric forms are obtained for the 5-complex numbers, which depend on the modulus, the amplitude and the angular variables. The 5-complex functions defined by series of powers are analytic, and the partial derivatives of the components of the 5-complex functions are closely related. The integrals of 5-complex functions are independent of path in regions where the functions are regular. The fact that the exponential form of the 5-complex numbers depends on the cyclic variables ϕ_1, ϕ_2 leads to the concept of pole and residue for integrals on closed paths. The polynomials of 5-complex variables can be written as products of linear or quadratic factors.

math.CV

Complex numbers in 6 dimensions

Two distinct systems of commutative complex numbers in 6 dimensions of the polar and planar types of the form u=x_0+h_1x_1+h_2x_2+h_3x_3+h_4x_4+h_5x_5 are described in this work, where the variables x_0, x_1, x_2, x_3, x_4, x_5 are real numbers. The polar 6-complex numbers introduced in this paper can be specified by the modulus d, the amplitude ρ, and the polar angles θ_+, θ_-, the planar angle ψ_1, and the azimuthal angles ϕ_1, ϕ_2. The planar 6-complex numbers introduced in this paper can be specified by the modulus d, the amplitude ρ, the planar angles ψ_1, ψ_2, and the azimuthal angles ϕ_1, ϕ_2, ϕ_3. Exponential and trigonometric forms are given for the 6-complex numbers. The 6-complex functions defined by series of powers are analytic, and the partial derivatives of the components of the 6-complex functions are closely related. The integrals of polar 6-complex functions are independent of path in regions where the functions are regular. The fact that the exponential form of ther 6-complex numbers depends on cyclic variables leads to the concept of pole and residue for integrals on closed paths. The polynomials of polar 6-complex variables can be written as products of linear or quadratic factors, the polynomials of planar 6-complex variables can always be written as products of linear factors, although the factorization is not unique.

math.CV

Polar complex numbers in n dimensions

Polar commutative n-complex numbers of the form u=x_0+h_1x_1+h_2x_2+...+h_{n-1}x_{n-1} are introduced in n dimensions, the variables x_0,...,x_{n-1} being real numbers. The polar n-complex number can be represented, in an even number of dimensions, by the modulus d, by the amplitude ρ, by 2 polar angles θ_+,θ_-, by n/2-2 planar angles ψ_{k-1}, and by n/2-1 azimuthal angles ϕ_k. In an odd number of dimensions, the polar n-complex number can be represented by d, ρ, by 1 polar angle θ_+, by (n-3)/2 planar angles ψ_{k-1}, and by (n-1)/2 azimuthal angles ϕ_k. The exponential function of a polar n-complex number can be expanded in terms of the polar n-dimensional cosexponential functions g_{nk}(y), k=0,1,...,n-1. Expressions are given for these cosexponential functions. The polar n-complex numbers can be written in exponential and trigonometric forms with the aid of the modulus, amplitude and the angular variables. The polar n-complex functions defined by series of powers are analytic, and the partial derivatives of the components of the polar n-complex functions are closely related. The integrals of polar n-complex functions are independent of path in regions where the functions are regular. The fact that the exponential form of a polar n-complex numbers depends on the cyclic variables ϕ_k leads to the concept of pole and residue for integrals on closed paths. The polynomials of polar n-complex variables can be written as products of linear or quadratic factors, although the factorization may not be unique.

math.CV

Planar complex numbers in even n dimensions

Planar commutative n-complex numbers of the form u=x_0+h_1x_1+h_2x_2+...+h_{n-1}x_{n-1} are introduced in an even number n of dimensions, the variables x_0,...,x_{n-1} being real numbers. The planar n-complex numbers can be described by the modulus d, by the amplitude ρ, by n/2 azimuthal angles ϕ_k, and by n/2-1 planar angles ψ_{k-1}. The exponential function of a planar n-complex number can be expanded in terms of the planar n-dimensional cosexponential functions f_{nk}, k=0,1,...,n-1, and expressions are given for f_{nk}. Exponential and trigonometric forms are obtained for the planar n-complex numbers. The planar n-complex functions defined by series of powers are analytic, and the partial derivatives of the components of the planar n-complex functions are closely related. The integrals of planar n-complex functions are independent of path in regions where the functions are regular. The fact that the exponential form of the planar n-complex numbers depends on the cyclic variables ϕ_k leads to the concept of pole and residue for integrals on closed paths. The polynomials of planar n-complex variables can always be written as products of linear factors, although the factorization may not be unique.

math.CV

Exponential forms and path integrals for complex numbers in n dimensions

Two distinct systems of commutative complex numbers in n dimensions are described, of polar and planar types. Exponential forms of n-complex numbers are given in each case, which depend on geometric variables. Azimuthal angles, which are cyclic variables, appear in these forms at the exponent, and this leads to the concept of residue for path integrals of n-complex functions. The exponential function of an n-complex number is expanded in terms of functions called in this paper cosexponential functions, which are generalizations to n dimensions of the circular and hyperbolic sine and cosine functions. The factorization of n-complex polynomials is discussed.

math.OA

Cross Sections for the Electron Activation of Gamma-Ray Fluorescence

We report cross sections for the direct excitation of gamma-ray transitions up to 200 keV by the transient electromagnetic fields of electrons from a beam, for incident kinetic energies of 500 keV and 5 MeV. The cross sections for the electron activation of gamma-ray fluorescence are of the order of 300 nanobarns for an electron incident kinetic energy of 500 keV, and are of the order of 10 microbarns for an electron incident kinetic energy of 5 MeV. The electron excitation of nuclear transitions may lead to the development of pulsed sources of gamma radiation of narrowly defined energy.

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Power densities for two-step gamma-ray transitions from isomeric states

We have calculated the incident photon power density P_2 for which the two-step induced emission rate from an isomeric nucleus becomes equal to the natural isomeric decay rate. We have analyzed two-step transitions for isomeric nuclei with a half-life greater than 10 min, for which there is an intermediate state of known energy, spin and half-life, for which the intermediate state is connected by a known gamma-ray transition to the isomeric state and to at least another intermediate state, and for which the relative intensities of the transitions to lower states are known. For the isomeric nucleus 166m-Ho, which has a 1200 y isomeric state at 5.98 keV, we have found a value of P_2=6.3 x 10^7 W cm^{-2}, the intermediate state being the 263.8 keV level. We have found power densities P_2 of the order of 10^{10} W cm^{-2} for several other isomeric nuclei.

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Induced Emission of Gamma Radiation from Isomeric Nuclei

We study the possibility to influence the lifetime of nuclear isomeric states with the aid of incident fluxes of photons. We assume that a nucleus initially in an isomeric state |i> first absorbs an incident photon of energy E_{ni} to reach a higher intermediate state |n>, then the state |n> decays to a lower state |l>. In favorable cases the two-step induced emission rates become equal to the natural isomeric decay rates for incident power densities of the order of 10^{10} W cm^{-2}.

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Essay on the gamma ray laser

This work discusses the possibility of inducing the emission of gamma radiation from nuclear isomers by two-photon transitions, in the more general context of the problem of the amplification of gamma radiation.

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Experimental conditions for the gamma optical scattering

This work discusses the possibility of observation of nuclear multiphoton processes in which the interaction of a gamma ray photon with a nucleus takes place simultaneously with the interaction of a radio-frequency photon.

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Amplification of Gamma Radiation from X-Ray Excited Nuclear States

In this paper we discuss the possibility of the excitation of nuclear electromagnetic transitions by the absorption of X-ray quanta produced in appropriate inner-shell atomic transitions, and the relevance of this process for the amplification of the gamma radiation from the excited nuclear states. It is concluded that the X-ray pumping technique might provide a useful approach for the development of a gamma ray laser.

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Integrated cross sections for two-photon transitions in 178-Hf

We have calculated integrated cross sections from tabulated nuclear data for two-photon transitions in 178-Hf, summed over all lower states which are possible for a given pair of initial and intermediate states. These processes are of interest for the problem of induced gamma emission. The largest integrated cross section found among 24 two-photon processes in 178-Hf has the value 1.65 x 10^{-26} cm^2 keV.

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Hypervelocity Impact Fusion with Compressed Deuterium-Tritium Targets

The neutron yields observed in inertial confinement fusion experiments for higher convergence ratios are about two orders of magnitude smaller than the neutron yields predicted by one-dimensional models, the discrepancy being attributed to the development of instabilities. We consider the possibility that ignition and a moderate gain could be achieved with existing laser facilities if the laser driver energy is used to produce only the radial compression of the fuel capsule to high densities but relatively low temperatures, while the ignition of the fusion reactions in the compressed fuel capsule will be effected by a synchronized hypervelocity impact. A positively-charged incident projectile can be accelerated to velocities of 3.5 x 10^6 m/s, resulting in ignition temperatures of about 4 keV, by a conventional low-beta linac having a length of 13 km if deuterium-tritium densities of 570 g/cm^3 could be obtained by laser-driven compression.

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