共查询到20条相似文献,搜索用时 31 毫秒
1.
Ian Affleck 《Nuclear Physics B》1981,185(2):346-364
The large-N limit of SU(N) matrix quantum mechanics has been studied recently as a model for large-N Yang-Mills theory. Here we solve this model with fundamental representation fermions (“quarks”) added. The “meson” spectrum is given by an integral equation and exhibits asymptotically linear “Regge trajectories” with the same spacing as that of the “glueballs”. 相似文献
2.
E. Z. Meilikhov R. M. Farzetdinova 《Journal of Experimental and Theoretical Physics》2010,110(5):794-804
Ferromagnetism of magnetic impurity atoms located in the barrier regions of various heterostructures (solitary heterojunction, single quantum well, double quantum well, or superlattice) is considered theoretically. The indirect magnetic interaction of impurities occurs via charge carriers localized in quasi-two-dimensional conducting channels of these structures due to “penetration” of the wavefunction of charge carriers into the barrier regions. The wavefunctions defined analytically in the triangular potential model are virtually the same as in “exact” numerical calculations (joint solution of the Poisson and Schrödinger equations). The corresponding Curie temperatures are determined, which may attain approximately 500 K in Ga1 ? x Mn x As-based structures according to calculations. 相似文献
3.
Electron tunneling through the GaN/Ga1?x AlxN(0001) wurtzite strained structures is investigated by the pseudopotential and scattering matrix methods. It is shown that the results of multiband calculations at low aluminum concentrations (x<0.3) are adequately described within the single-valley model in the envelope wave function method accounting for the dependences of the effective mass on the energy and strain. Upon electron tunneling through two-barrier structures, sharp resonance peaks are observed at a barrier thickness of several monolayers and the characteristic collision time in the resonance region is equal to ~1 ps. The internal electric fields associated with spontaneous and piezoelectric polarizations lead to a “red” or “blue” shift in the resonance energy according to the thickness and location of barriers with respect to the polar axis. In the (GaN)n(Ga1?x AlxN)m superlattices, the internal fields can form the Stark ladder of electronic states at a small number of ultrathin layers even in the absence of external fields. 相似文献
4.
In a high resolution laser excitation spectrum of NO2, lines were recorded which do not follow the selection rule ΔN = ΔJ = ΔF of “spin allowed” transitions. Line positions and intensities of these “spin forbidden” lines were investigated for all rotational lines up to N″ = 12 of the Ka = 0 subband around λ = 592.5 nm. While the observed line intensities of “spin allowed” transitions can be well described by the J-coupling scheme, neither the J- nor the G-coupling scheme sufficiently describes the “spin forbidden” transitions. The observations can be fitted satisfactorily by perturbation theory, in which the Fermi interaction in 2A1 is treated as the perturber. This looks similar to a superposition of J and G scheme in the 2A1 ground state. 相似文献
5.
O. I. Velikokhatnyi S. V. Eremeev I. I. Naumov A. I. Potekaev 《Journal of Experimental and Theoretical Physics》2000,90(3):479-487
The nature of the stability of incommensurate long-period structures in alloys of the system Cu-Au is investigated on the basis of first-principles calculations of the electronic structure. It is shown that many structural properties of such formations can be explained only if the latter are treated as superstructures with respect to ordinary superstructures (L12 or L10): the electron spectrum of the superstructure and not that of the initial disordered alloy must serve as the initial spectrum. The observed dependence of the long period N on the degree η ?of the “short” long-range order is explained. The reasons why two-dimensional long-period superstructures from in the alloy Au3Cu are found. Arguments supporting the fact that among quasicrystalline substances long-period superstructures fall between incommensurate systems and quasicrystals are presented. 相似文献
6.
7.
The high resolution infrared spectrum of N2O in the region of ν2 has been studied with a Fourier transform spectrometer at a resolution of (about) 0.005 cm?1 and an accuracy of about ±0.00005 cm?1. In addition to ν2, “hot” bands associated with this band and the bending fundamental ν2 of 15N14N16O and 14N15N16O were analyzed. 相似文献
8.
9.
Self-consistent computations of the monovacancy formation energy are performed for Na N , Mg N , and Al N (12 < N ≤ 168) spherical clusters in the drop model for stable jelly. Scenarios of the Schottky vacancy formation and “bubble vacancy blowing” are considered. It is shown that the asymptotic behavior of the size dependences of the energy for the vacancy formation by these two mechanisms is different and the difference between the characteristics of a charged and neutral cluster is entirely determined by the difference between the ionization potentials of clusters and the energies of electron attachment to them. 相似文献
10.
A new set of donor and acceptor ionization energies in GaP is deduced from photoexcitation spectra. Energy spectrum of donor states confirms an existence of the “camel's back” with a conduction band minima displacement ≈ 0.08(2π/a) from the X, and the corresponding energy shift ≈ 3meV. The free exciton binding energy in GaP is correctly determined: Eex = 21 ± 2 meV. 相似文献
11.
The rotational spectra of αd1- and αd2-ortho-fluorotoluene in the ground state of the methyl group torsion have been measured. The evaluation of the spectra has been based on the theory for the internal rotation of an asymmetric internal top formulated earlier by several authors. The barrier potential being threefold symmetric (V3), each torsional level consists of three nondegenerate substates, designated as sy and ±asy. The sy-state is assigned to the conformation with the unique methyl hydrogen isotope within the molecular heavy-atom plane (sy-rotamer), while the ±asy-states belong to the respective out-of-plane conformation (asy-rotamer). In the torsional ground state the level spacing between the ±asy substates is very small and numerous accidental close degeneracies are present between the rotational level systems based on these torsional substates. The rotational levels involved are strongly perturbed by the coupling between molecular overall rotation and internal rotation. Large deviations from a rigid rotor spectrum and (+) ? (?) intersystem (“tunneling”) transitions are observed. The spectrum of the asy-rotamer can be well reproduced by a “two-dimensional” Hamiltonian containing 11 “rotational constants,” 9 of which are determined by a fit to the spectrum. Several are sufficiently barrier-dependent to derive V3. We obtain (in cal/mole) 567 ± 48 for αd1-ortho-fluorotoluene, 711 ± 40 for the αd2-isotope. The deviations from 649 cal/mole for the normal isotope are appreciable, probably indicating shortcomings of the semirigid model. The sy-rotamer presents a rigid rotor spectrum. 相似文献
12.
The microwave “a” and “c” type spectra of four isotopic species of CH3NHCl in the ground state and of CH3NHCl35 and CH3NDCl35 in the first excited torsional state have been analyzed. From the A-E torsional splittings of the excited state the torsional barrier height has been determined to be V3 = 3710 ± 46 cal/mole. The “c” type transitions show an inversion doubling of 4.60 ± 0.10 MHz in the ground state and of 5.25 ± 0.10 MHz in the first excited torsional state. Such doublings are independent on the rotational quantum numbers within the experimental errors. The height of the inversion barrier has been roughly evaluated by using the Dennison-Uhlenbeck potential. 相似文献
13.
14.
For the giant 4d photoabsorption of La, both the total photoabsorption spectrum and the N4.5-derived Auger emission intensity spectrum increase significantly above hν ? 112 eV, with spectral peaks at hν = 118 and 119 eV, respectively. However, the predominant 4d photoemission partial cross section shows a delayed onset of ~ 4 eV, with a peak at hν = 121 eV, while the 5s, 5p, and 5d partial cross sections all show a strong resonant enhancement at lower energies, with spectral peaks at hν = 116.6 eV. These results are compared with a recent many-body calculation for Ce. The photon energy dependence of the La 4d/4d photo-emission branching ratio is consistent with a “final-state model.” 相似文献
15.
Martin Jesús Soberón Mobarak 《Hyperfine Interactions》2005,161(1-4):185-190
Anelastic behavior of crystalline solids is generated by several microstructural processes. Its experimental study yields valuable information about materials, namely: modulus, dissipation mechanisms and activation enthalpies. However, conventional techniques to evaluate it are complicated, expensive, time consuming and not easily replicated. As a new approach, in this work a Mössbauer spectrum of an iron specimen is obtained with the specimen at repose being its parameters the “base parameters.” After that, the same specimen is subjected to an alternated stress–relaxation cycle at frequency ω 1 and a new Mössbauer spectrum is obtained under this excited condition; doing the same at several increasing frequencies ω n in order to scan a wide frequencies spectrum. The differences between the Mössbauer parameters obtained at each excitation frequency and the base parameters are plotted against frequency, yielding an “anelastic spectrum” that reveals the different dissipation mechanisms involved, its characteristic frequency and activation energy. Results are in good agreement with the obtained with other techniques 相似文献
16.
V. P. Maslov 《Russian Journal of Mathematical Physics》2016,23(4):510-528
We show how the abstract analytic number theory of Maier, Postnikov, and others can be extended to include negative numbers and apply this to thermodynamics, information theory, and human thermodynamics. In particular, we introduce a certain large number N 0 on the “zero level” with a high multiplicity number q i ? 1 related to the physical concept of gap in the spectrum. We introduce a general notion of “hole,” similar to the Dirac hole in physics, in the theory. We also consider analogs of thermodynamical notions in human thermodynamics, in particular, in connection with the role of the individual in history. 相似文献
17.
Simone Giombi Shiraz Minwalla Shiroman Prakash Sandip P. Trivedi Spenta R. Wadia Xi Yin 《The European Physical Journal C - Particles and Fields》2012,72(8):1-65
We study three-dimensional conformal field theories described by U(N) Chern?CSimons theory at level k coupled to massless fermions in the fundamental representation. By solving a Schwinger?CDyson equation in light-cone gauge, we compute the exact planar free energy of the theory at finite temperature on ?2 as a function of the ??t?Hooft coupling ??=N/k. Employing a dimensional reduction regularization scheme, we find that the free energy vanishes at |??|=1; the conformal theory does not exist for |??|>1. We analyze the operator spectrum via the anomalous conservation relation for higher spin currents, and in particular show that the higher spin currents do not develop anomalous dimensions at leading order in 1/N. We present an integral equation whose solution in principle determines all correlators of these currents at leading order in 1/N and present explicit perturbative results for all three-point functions up to two loops. We also discuss a light-cone Hamiltonian formulation of this theory where a W ?? algebra arises. The maximally supersymmetric version of our theory is ABJ model with one gauge group taken to be U(1), demonstrating that a pure higher spin gauge theory arises as a limit of string theory. 相似文献
18.
Sh.B. Atakulov 《Solid State Communications》1984,51(6):415-419
The peculiarities of the potential shape in polycrystalline films were considered. It was shown that the barrier height (φB) in sites (the place where three or more crystallites are connected) with respect to the concentration of boundary states (BS) was higher or coincided with the barrier height (φA) at the crystallite boundaries (CB). That is why the sites for majority charge carriers in films were “blocked down” and current transport along CB was not realized. If inversion of the conductivity type at CB was absent, the Hall potential was generated in quasi-neutral regions of crystallites and in barrier regions perpendicular to the current lines. If the Hall potential coefficient (RH) of the film is determined by the carrier concentration n0 in quasi-neutral regions. In this case the activation energy of the Hall mobility was equal to the activation energy of the conductivity (σA). In the opposite case the inversion conductivity type takes place on CB. When the inversion regions are present near the barrier tops and conductivity is realized along CB, RHp ~ (NcNv/n0)-1 exp (Eg?φB/kT) and μHp ~ exp (?φB?φA/kT), where Eg is the band gap, Nc, Nv are the effective density of states in the conduction and valence bands. 相似文献
19.
Au/silicon nitride/In0.82Al0.18As metal insulating semiconductor (MIS) capacitors were fabricated and then investigated by capacitance voltage (C–V) test at variable frequencies and temperatures. Two different technologies silicon nitride (SiNx) films deposited by inductively coupled plasma chemical vapor deposition (“ICPCVD”) and plasma enhanced chemical vapor deposition (“PECVD”) were applied to the MIS capacitors. Fixed charges (Nf), fast (Dit) and slow (Nsi) interface states were calculated and analyzed for the different films deposition MIS capacitors. The Dit was calculated to be 4.16 × 1013 cm−2 eV−1 for “ICPCVD” SiNx MIS capacitors, which was almost the same to that of “PECVD” SiNx MIS capacitors. The Dit value is obviously higher for the extended wavelength InxGa1−xAs (x > 0.53) epitaxial material as a result of lattice mismatch with substrate. Compared to the results of “PECVD” SiNx MIS capacitors, the Nsi was significantly lower and the Nf was slightly lower for “ICPCVD” SiNx MIS capacitors. X-ray photoelectron spectroscopy (XPS) analysis shows good quality of the “ICPCVD” grown SiNx. The low temperature deposited SiNx films grown by “ICPCVD” show better effect on decreasing the dark current of InxGa1−xAs photodiodes. 相似文献
20.
Michael K.-H. Kiessling 《Journal of statistical physics》2009,137(5-6):1063-1078
The N-dependence of the non-relativistic bosonic ground state energy ? B (N) is studied for quantum N-body systems with either Coulomb or Newton interactions. The Coulomb systems are “bosonic atoms,” with their nucleus fixed, and it is shown that $\mathcal {E}_{{C}}^{{B}}(N)/\mathcal {P}_{{C}}(N)$ grows monotonically in N>1, where ? C (N)=N 2(N?1). The Newton systems are “bosonic stars,” and it is shown that when the Bosons are centrally attracted to a fixed gravitational “grain” of mass M>0, and N>2, then $\mathcal {E}_{{N}}^{{B}}(N;M)/\mathcal {P}_{\!{N}}(N)$ grows monotonically in N, where ? N (N)=N(N?1)(N?2); in the translation-invariant problem (M=0), it is shown that when N>1 then $\mathcal {E}_{{N}}^{{B}}(N;0)/\mathcal {P}_{{C}}(N)$ grows monotonically in N, with ? C (N) from the Coulomb problem. Some applications of the new monotonicity results are discussed. 相似文献