检索结果-南通市图书馆

Maximum mass of magnetic white dwarfs

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2015年第10期15卷 1735-1741页

作者： Daryel Manreza Paret Jorge Ernesto Horvath Aurora Pérez Martínez departamento de fisica General Facultad de FísicaUniversidad de la Habana instituto de Astronomia Geofisica e Ciencias Atmosfericas USP instituto de Cibernética Matemática y Física(ICIMAF)

We revisit the problem of the maximum masses of magnetized white dwarfs （WDs）. The impact of a strong magnetic field on the structure equations is addressed. The pressures become anisotropic due to the presence of the magnetic field and split into parallel and perpendicular components. We first construct stable solutions of the Tolman-Oppenheimer-Volkoff equations for parallel pressures and find that physical solutions vanish for the perpendicular pressure whenB ≥ 10^13 G. This fact estab- lishes an upper bound for a magnetic field and the stability of the configurations in the （quasi） spherical approximation. Our findings also indicate that it is not possible to obtain stable magnetized WDs with super-Chandrasekhar masses because the val- ues of the magnetic field needed for them are higher than this bound. To proceed into the anisotropic regime, we can apply results for structure equations appropriate for a cylindrical metric with anisotropic pressures that were derived in our previous work. from the solutions of the structure equations in cylindrical symmetry we have con- firmed the same bound for B- 10^13 G, since beyond this value no physical solutions are possible. Our tentative conclusion is that massive WDs with masses well beyond the Chandrasekhar limit do not constitute stable solutions and should not exist.

关键词： magnetic fields -- white dwarfs -- equation of state

A generalization of the half-normal distribution

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2016年第4期31卷 409-424页

作者： yolanda M. Gomez Ignacio Vidal departamento de matemáticas facultad de ciencias universidad de católica del norte Antofagasta Chile instituto de matemática y física universidad de talca Chile

In this paper we introduce an extension of the half-normal distribution in order to model a great variety of non-negative data. Its hazard rate function can be decreasing or increasing, depending on its parameters. Some properties of this new distribution are presented. for example, we give a general expression for the moments and a stochastic representation. Also, the cumulative distribution function, the hazard rate function, the survival function and the quantile function can be easily evaluated. Maximum likelihood estimators can be computed by using numerical procedures. finally, a real-life dataset has been presented to illustrate its applicability.

关键词： half-normal distribution generalized half-normal distribution maximum likelihood estimate

Variational Calculus With Conformable fractional derivatives

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2017年第2期4卷 340-352页

作者： Matheus J.Lazo delfim f.M.Torres instituto de matemática Estatística e Física-FURG Center for Research and development in Mathematics and Applications (CIDMA) Department of MathematicsUniversity of Aveiro

Invariant conditions for conformable fractional problems of the calculus of variations under the presence of external forces in the dynamics are studied. depending on the type of transformations considered, different necessary conditions of invariance are obtained. As particular cases, we prove fractional versions of Noether's symmetry theorem. Invariant conditions for fractional optimal control problems, using the Hamiltonian formalism, are also investigated. As an example of potential application in Physics, we show that with conformable derivatives it is possible to formulate an Action Principle for particles under frictional forces that is far simpler than the one obtained with classical fractional derivatives.

关键词： Conformable fractional derivative fractional calculus of variations fractional optimal control invariant variational conditions Noether’s theorem

Quantum information entropies of the eigenstates for the Pschl-Teller-like potential

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2013年第5期22卷 113-117页

作者： Guo-Hua Sun M. Avila Aoki Shi-Hai Dong Centro Universitario Valle de Chalco Universidad Autónoma del Estado de México departamento de física Escuela Superior de Física y MatemáticsInstituto Politécnico Nacional

Shannon entropy for lower position and momentum eigenstates of Ptschl-Teller-like potential is evaluated. Based on the entropy densities demonstrated graphically, we note that the wave through of the position information entropy density p （x） moves right when the potential parameter V1 increases and its amplitude decreases. However, its wave through moves left with the increase in the potential parameter 丨V2丨. Concerning the momentum information entropy density p（p）, we observe that its amplitude increases with increasing potential parameter V1, but its amplitude decreases with increasing丨V2丨. The Bialynicki-Birula-Mycielski （BBM） inequality has also been tested for a number of states. Moreover, there exist eigenstates that exhibit squeezing in the momentum information entropy. finally, we note that position information entropy increases with V1, but decreases with 丨V2丨, However, the variation of momentum information entropy is contrary to that of the position information entropy.

关键词： bound states quantum information entropy Poschl-Teller-like potential

Inequalities for the Extended Best Polynomial Approximation Operator in Orlicz Spaces

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2019年第2期35卷 185-203页

作者： Sonia ACINAS Sergio fAVIER felipe ZO departamento de matemática Facultad de Ciencias y Exactas NaturalesUniversidad Nacional de La Pampa instituto de matemática Aplicada San Luis IMASLUniversidad Nacional de San Luis and CONICET departamento de matemática Universidad Nacional de San Luis

In this paper we pursue the study of the best approximation operator extended from L~Φ to L~φ, where φ denotes the derivative of the function Φ. We get pointwise convergence for the coefficients of the extended best approximation polynomials for a wide class of function f, closely related to the Calder′on–Zygmund class t_m^p(x) which had been introduced in 1961. We also obtain weak and strong type inequalities for a maximal operator related to the extended best polynomial approximation and a norm convergence result for the coefficients is derived. In most of these results, we have to consider Matuszewska–Orlicz indices for the function φ.

关键词： Orlicz spaces extended best polynomial approximation pointwise and norm convergence weak and strong type inequalities Orlicz indices

Complementarity between quantum coherence and mixedness:a majorization approach

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2023年第5期75卷 73-83页

作者： yanet Alvarez Marcelo Losada Mariela Portesi Gustavo M Bosyk instituto de física La Plata CONICET–UNLP1900 La PlataArgentina facultad de Ciencias Exactas Universidad Nacional de La Plata1900 La PlataArgentina facultad de matemática AstronomíaFísica y ComputaciónUniversidad Nacional de Córdoba5000 CórdobaArgentina

Quantum coherence is a relevant resource for various quantum information processing tasks,but it is fragile since it is generally affected by environmental *** is reflected in the loss of purity of the system,which in turn limits the amount of quantum coherence of *** a consequence,a complementarity relation between coherence and mixedness *** works characterize this complementarity through inequalities between theℓ1-norm of coherence and linear entropy,and between the relative entropy of coherence and von Neumann ***,coherence-mixedness complementarity is expected to be a general feature of quantum systems,regardless of the measures ***,an alternative approach to coherence-mixedness complementarity,based on majorization theory,is *** quantifiers of coherence and mixedness,namely the coherence vector and the spectrum,respectively,are used,instead of scalar measures.A majorization relation for the tensor product of both vectorial quantifiers is obtained,capturing general aspects of the trade-off between coherence and *** optimal bound for qubit systems and numerical bounds for qutrit systems are ***,coherence-mixedness complementarity relations are derived for a family of symmetric,concave and additive *** results provide a deeper insight into the relation between quantum coherence and mixedness.

关键词： coherence mixedness complementarity majorization

Analytic solutions of the double ring-shaped Coulomb potential in quantum mechanics

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2013年第10期22卷 94-100页

作者：陈昌远陆法林孙东升董世海 School of Physics and Electronics Yancheng Teachers University departamento de física Escuela Superior de Física y MatemticasInstituto Politcnico NacionalEdificio 9Unidad Profesional Adolfo López MateosMexico D.F.07738Mexico

The exact solutions of the Schr6dinger equation with the double ring-shaped Coulomb potential are presented, including the bound states, continuous states on the ＂k/2π scale＂, and the calculation formula of the phase shifts. The polar angular wave functions are expressed by constructing the so-called super-universal associated Legendre polynomials. Some special cases are discussed in detail.

关键词： double ring-shaped Coulomb potential super-universal associated-Legendre polynomial functional analysis method

Relativistic Treatment of Spinless Particles Subject to a Rotating deng-fan Oscillator

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2011年第6期55卷 969-971页

作者：董世海 departamento de física Escuela Superior de Física y MatemáticasInstituto Politécnico NacionalEdificio 9Unidad Profesional Adolfo López MateosMexico D.F.07738Mexico

The bound state solutions of the Klein-Gordon equation with the rotating deng-fan molecular potential are presented by using a proper approximation to the centrifugal term within the framework of equal scalar and vector deng-fan potentials. It is shown that the solutions can be expressed by the generalized hypergeometric functions. The normalized wavefunctions are also derived.

关键词： Klein-Gordon equation deng-fan oscillator centrifugal term

Quantum Instability of Magnetized Stellar Objects

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2005年第4期5卷 399-411页

作者： R.González felipe H.J.Mosquera Cuesta A.Pérez Martínez H.Pérez Rojas departamento de física and Centro de física Teórica de Partículas Instituto Superior TécnicoAv.Rovisco Pais1049-001 LisboaPortugal instituto de Cosmologia Relatividade e Astrofísica(ICRA-BR)Centre Brasileiro de Pesquisas FísicasRua Dr.Xavier Sigaud 150CEP 22290-180UreaRio de JaneiroRJBrazil Centro Latino-Americano de física Avenida Wenceslau Braz 71CEP 22290-140 fundosBotafogoRio de JaneiroBrazil instituto de Cibernética Matemática y FísicaCalle E No.30910400 La HabanaCuba

The equations of state for degenerate electron and neutron gases are studied in the presence of magnetic *** including quantum effects in the investigation of the structural properties of these systems,it is found that some hypermagnetized stars can be unstable according to the criterion of stability of *** magnetized white dwarfs should collapse producing a supernova type Ia,while superstrong magnetized neutron stars cannot stand their own magnetic field and must implode,too.A comparison of our results with a set of the available observational data of some compact stars is also presented,and the agreement between this theory and observations is verified.

关键词： dense matter-equation of state-instabilities-stars:magnetic fields-stars:neutron white dwarfs