共查询到20条相似文献,搜索用时 451 毫秒
1.
David B. Reiss 《Physics letters. [Part B]》1982,115(3):217-220
We consider the possibility that the family group may be a spontaneously broken continuous global symmetry. In the context of grand unification, the couplings of the associated Goldstone bosons to fermions can be sufficiently suppressed so as to satisfy the phenomenological bounds. For a maximal family symmetry this requires a large number of Higgs fields. 相似文献
2.
E.P. Bashkin 《Physics letters. A》1978,69(4):282-284
It is shown on the basis of the experimental data on thermodynamic and transport properties under pressure that the temperatures of the transition of 3He to the superfluid state for 3He-4He solutions with concentrations 0.6-3% lie in the range 0.4–1.4 mK. 相似文献
3.
It is stressed that within the simplest model SU(4) of color, unifying quarks with leptons, where B L is a gauge symmetry, a spontaneous breaking of this symmetry leads naturally to baryonlepton decays like n→e?k+, e?K+, μ?π+, μ?K+ [in constant to SU(5) where B L is not gauged]. Our mechanism is crucially tied to the presence of the Higgs multiplet (2, 2, 15) of SU(2) × SU(2) × SU(4), which is needed to account for the observed quarklepton mass ratios. 相似文献
4.
We have cooled a 3He4He solution to the lowest temperatures yet achieved, 0.58 mK, and find no evidence for a superfluid transition in the dissolved 3He. We have measured the thermal boundary resistance between this solution and sintered 700 Å silver powder, and find that R is proportional to T?2 between 0.8 mK and 4 mK. 相似文献
5.
E. Østgaard 《Physics letters. A》1974,49(6):433-434
The possibility of superfluidity of 3He in dilute solutions of 3He in liquid 4He is investigated, and the corresponding critical temperature is estimated. The results indicate S-state pairing, i.e., for small concentrations of 3He, the highest transition temperature is obtained for L = 0, but the obtained critical temperatures are very low. 相似文献
6.
C.R. Ottermann G. Köbschall K. Maurer K. Röhrich Ch. Schmitt V.H. Walther 《Nuclear Physics A》1985,436(4):688-698
The cross sections for elastic electron scattering from 3He and 4He were measured for the momentum transfer range from 0.45–2.0 fm?1. The cross sections were separated into their longitudinal (charge) and transverse (magnetic) contributions using the Rosenbluth formula. The charge and magnetic form factors were obtained model-independently.The rms charge radii were found to be 1.671 (14) fm for 4He and 1.976 (15) fm for 3He, and the magnetic rms radius of 3He is 1.99 (6) fm. The mis charge radius for 4He is in excellent agreement with the latest muonic data.Comparison of the form factors was made with Faddeev three-body calculations using realistic two-body NN interactions. At present the theoretical calculation is not able to reproduce the experimental data. 相似文献
7.
C.M. Varma 《Physics letters. A》1973,45(4):301-302
It is suggested that at a wave vector near the inverse average interparticle separation, the spectrum of a 3He atom in superfluid 4He has a roton like dip. The results of light scattering and transport measurements in liquid 3He-4He mixtures can thereby be reconciled. 相似文献
8.
We propose a new class of leptogenesis bounds on the spontaneous symmetry breaking of global lepton number. These models have
a generic feature of inducing new lepton number violating interactions, due to the presence of the Majorons. We analyzed the
singlet Majoron model with right-handed neutrinos to find that the lepton number should be broken above 105 GeV to realize a successful leptogenesis because the annihilations of the right-handed neutrinos into the massless Majorons
and into the standard model Higgs should go out of equilibrium before the sphaleron process is over. We then argue that this
type of leptogenesis constraint should exist in the singlet–triplet Majoron models as well as in a class of R-parity violating
supersymmetric Majoron models. 相似文献
9.
10.
The Bose spectrum of superfluid solutions 3He4He is investigated in the case of p-pairing of Fermi particles. Both three-dimensional and two-dimensional models are considered. It is shown that the Bose-Fermi interaction changes the sound velocities in both subsystems. The other collective modes (17 in the 3D-model and 11 in the 2D-model) remain almost unchanged. 相似文献
11.
Thermal conductivities and thermodiffusion ratios in a number of 3He4He mixtures near the lambda line have been found to show peak temperature dependences as expected from the mode coupling theory. 相似文献
12.
《Physics letters. [Part B]》1987,183(1):71-74
We investigate the possibility of maintaining the hierarchy of the gauge and lepton number symmetry breakdown in the context of the Gelmini-Roncadelli model of electroweak interactions. Calculating the effective potential in the one-loop approximation, we find the additional constraints one must impose on the scalar self-couplings to protect the tree level hierarchy from dangerous radiative corrections. 相似文献
13.
J. Källne J. Davis R.C. Minehart R.R. Whitney R.L. Boudrie J. McClelland A.W. Stetz 《Physics letters. [Part B]》1980,97(2):205-208
Results are presented for π+NN → Np yields in 3,4He relative to πd → pp from (π, p) measurements at energies between 50 and 295 MeV and estimates are given for total cross sections. These yields are nearly proportional to the number of target NN pairs, which is not true for 6Li and heavier nuclei. This is believed to indicate that πNN → Np is sensitive to the NN short-range behavior which is deuteron-like for 3,4He but not always so for NN pairs in other nuclei. 相似文献
14.
Angular distributions of the polarization in the elastic scattering of 3He by 3He have been measured at eight energies between 18 and 33 MeV, corresponding to excitation of 6Be between 20.5 and 28 MeV. The measurements were made using the 33 MeV polarised 3He beam at the University of Birmingham Radial Ridge cyclotron and a small gas target. The data have been analysed in terms of real and complex phase shifts. The deduced phase shift energy dependence cannot be associated with a single isolated level in 6Be, however an application of the two-level R-matrix formula reveals some broad L = 3 structures around Ex = 25 MeV. 相似文献
15.
We develop the quasiclassical theory for normal and superfluid liquid 3He using a systematic expansion in small parameters such as δ/EF, ?0?1/kF, etc., and paying particular attention to the high-energy renormalizations of the external pertubations and observables. We apply the general formalism to a number of more specific problems including the derivation of the non-linear quantum kinetic equation for normal 3He, the weak-coupling and strong-coupling free energies and static response functions for superfluid 3He, and the low-frequency and high-frequency dynamics of the superfluid phases. We also discuss extensions of the quasiclassical framework to cover strong short-ranged pertubations such as walls and ions, review recent phenomenological models for the quasiparticle scattering amplitude, and present a brief but self-contained derivation of the Keldysh perturbation theory for real-time Green's functions. 相似文献
16.
The energies of the bound 0+ states of the α-particle are calculated on the basis of four body integral equations with separable 1S0 and 3S1 pair interactions. We find the ground state at z1 = ?45.73 MeV and an excited o+ level is found to be ?11.69 MeV. 相似文献
17.
A model is proposed to describe the near-threshold production of pions in the reaction. Taking experimental data on the He process as input the cross sections for the first three levels of 6Li are reproduced semi-quantitatively. 相似文献
18.
A monolayer of 4He atoms is treated as a system of hard-sphere bosons in a thin film geometry, with a finite thickness. The method of pseudopotential is used to calculate first the energy spectrum, and then the Helmholtz free energy and other thermodynamic functions of the system. It is found that Bose-Einstein condensation exists below a definite temperature. Much like a liquid-gas transition, the boson system displays a high temperature normal phase, a low temperature condensed superfluid phase and coexistence region. In the present treatment, the minimum momentum associated with the finite thickness of monolayer is used as a parameter. We find that the transition temperature is linearly proportional to the density of the 4He film. After performing double-tangent construction of the Helmholtz free energy curve we find for the specific heat a rounded peak at the transition temperature, in agreement with recent experiments. The ratio of the superfluid density at the transition point to the transition temperature is found to be essentially a constant. 相似文献
19.
Differential cross sections for 3He + 3He elastic scattering are calculated at c.m. energies from 2.95 to 37.44 MeV using the one-channel resonating-group method. A phenomenological imaginary potential, whose strength depends on whether the relative orbital angular momentum is even or odd, is included in order to account approximately for open reaction channels. The introduction of such an odd-even feature leads to a significantly improved agreement with experiment, especially at the larger scattering angles. In addition, an analysis of the calculated resonant phase shifts confirms recent experimental observations of highly excited levels in 6Be. 相似文献
20.
The quasiparticle interaction in liquid 3He is studied. It is shown that part of the interaction can be considered induced through the exchange of density and spin-density excitations. The coupling of these excitations to quasiparticles is shown to be given rigorously by the quasiparticle interaction itself in the long wavelength limit. The induced part of the interaction is then calculated by determining the density-density and spin-density-spin-density response functions assuming that the irreducible particle-hole vertex functions are frequency independent. The remainder of the interaction is shown to be given by a vertex function which does not have certain singularities and it is argued that it can be approximated by the Brueckner G-matrix. From the net interaction Landau parameters are extracted and compared with the experimentally known ones. Since the agreement was not satisfactory, the consequences of making a theory in terms of “paramagnons” is explored. This leads to much better numerical results, but the theory is less satisfactory. Consideration of the density-density response function arrived at here shows it to be similar to one proposed by Pines and Nozières [3, 24], who assumed a local relation between a density fluctuation and the potential it produces. We come to the conclusion that the numerical discrepancies between our calculated Landau parameters and the experimental ones probably arise from neglect of the exchange of two and more spin fluctuations. In the paper following this one, O. Sjöberg makes application of our theory to calculate the Landau parameters of nuclear matter. No “soft” excitations such as the spin fluctuations of liquid 3He exist in nuclear matter, and the theory appears to be quantitatively much better there, although some of the crucial Landau parameters are not directly measurable, and a direct check is not possible. 相似文献