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1.
We discuss a supersymmetric model with discrete flavor symmetry A_4×Z_3. The additional scalar fields which contribute masses of leptons in the Yukawa terms are introduced in this model. We analyze their scalar potential and find that they have various vacuum structures. We show the relations among 24 different vacua and classify them into two types. We derive expressions of the lepton mixing angles, Dirac CP violating phase and Majorana phases for the two types. The model parameters which are allowed by the experimental data of the lepton mixing angles are different for each type. We also study the constraints on the model parameters which are related to Majorana phases. The different allowed regions of the model parameters for the two types are shown numerically for a given region of two combinations of the CP violating phases.  相似文献   

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We study solitons in a spin-1 Bose–Einstein condensates with SU(3) spin–orbit coupling. We obtain the ground state and the metastable solution for solitons with attractive interactions by the imaginary-time evolution method. Compared with the SU(2) spin–orbit coupling, it is found that the solitons in SU(3) spin–orbit coupling show a new feature due to breaking the symmetry. The solitons called the composite solitons have mixing manifolds of ferromagnetic and antiferromagnetic states. This has stimulated people to study the topological excitation properties of SU(3) spin–orbit coupling and it is expected to find new quantum phases.  相似文献   

4.
If the neutrino mass spectrum turns out to be m_3 m_1 m_2, it may be relabeled as m_1 m_2 m_3 such that all the masses of fundamental fermions with the same electrical charges are in order. In this case the columns of the 3×3 lepton flavor mixing matrix U should be reordered accordingly, and the resulting pattern U may involve one or two large mixing angles in the standard parametrization or its variations. Since the Majorana neutrino mass matrix remains unchanged in such a mass relabeling, a possible μ-τ reflection symmetry is respected in this connection and its breaking effects are model-independently constrained at the 3σ level by using current experimental data.  相似文献   

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杨红  张廷桂  张岩 《中国物理 B》2017,26(2):24204-024204
We have studied the probe gain via a double-Λ atomic system with a pair of closely lying lower levels in the presence of two probe and two coherent pump fields. The inversionless gain can be realized by using nondegenerate four-wave mixing under the condition of spontaneously generated coherence(SGC) owing to near-degenerate lower levels. Note that by using SGC, two probe fields can be amplified with more remarkable amplitudes, and the gain spectra of an extremely narrow linewidth can be obtained. Last but not least, our results show that the probe gain is quite sensitive to relative phases due to the SGC presence which allows one to modulate the gain spectra periodically by phase modulation, and can also be influenced by all laser field intensities and frequencies, and the angles between dipole elements.  相似文献   

7.
《理论物理通讯》2020,72(4):45-51
We study the complex Berry phases in non-Hermitian systems with parity-and time-reversal(PT) symmetry.We investigate a kind of two-level system with PT symmetry.We find that the real part of the the complex Berry phases have two quantized values and they are equal to either 0 or Π,which originates from the topology of the Hermitian eigenstates.We also find that if we change the relative parameters of the Hamiltonian from the unbroken-PT-symmetry phase to the broken-PT-symmetry phase,the imaginary part of the complex Berry phases are divergent at the exceptional points.We exhibit two concrete examples in this work,one is a two-level toys model,which has nontrivial Berry phases;the other is the generalized Su-Schrieffer-Heeger(SSH) model that has physical loss and gain in every sublattice.Our results explicitly demonstrate the relation between complex Berry phases,topology and PT-symmetry breaking and enrich the field of the non-Hermitian physics.  相似文献   

8.
Based on a linear sigma model, we discuss the mixing between a quark condensate and a gluon condensate. It is shown that the linear sigma model will not be self-consistent if we switch off the mixing coupling between glueball and chiral fields. By introducing a proper mixing coupling, we realize the second-order phase transitions of chiral symmetry restoration and deconfinement. We further show that the critical temperature of chirM symmetry restoration could not be larger than the temperature of deconfinement phase transition in all possible parameter spaces of our model.  相似文献   

9.
Quantum criticality is closely related to the existence of two phases with unrelated symmetry breaking. In this paper,we study Néel and Kekulé valence bond state(VBS) quantum criticality in Dirac semimetals with four-fermion interactions.Our results show that all possible dynamical masses yield the same critical coupling, which exhibits the phenomenon that all possible phases meet at a multicritical point(e.g., a tricritical point for the Néel, Kekulé-VBS and semimetallic phases).In terms of the well-established Wess–Zumino–Witten field theory, we investigate the typical criticality for the transition between Néel and Kekulé-VBS phases, and the compatible Néel–Kekulé-VBS mass matrices imply the existence of a nonLandau transition between the Néel and Kekulé-VBS phases. We show the existence of mutual duality in the defect-driven Néel–Kekulé-VBS transition near the non-Landau critical point and find that this mutual duality results from the presence of a mutual Chern–Simons term. We also study the mutual duality based on dual topological excitations.  相似文献   

10.
We investigate the properties of Bose–Einstein condensates(BECs) in a two-dimensional quasi-periodic optical lattice(OL) with eightfold rotational symmetry by numerically solving the Gross–Pitaevskii equation. In a stationary external harmonic trapping potential, we first analyze the evolution of matter-wave interference pattern from periodic to quasiperiodic as the OL is changed continuously from four-fold periodic to eight-fold quasi-periodic. We also investigate the transport properties during this evolution for different interatomic interaction and lattice depth, and find that the BEC crosses over from ballistic diffusion to localization. Finally, we focus on the case of eightfold symmetric lattice and consider a global rotation imposed by the external trapping potential. The BEC shows vortex pattern with eightfold symmetry for slow rotation, becomes unstable for intermediate rotation, and exhibits annular solitons with approximate axial symmetry for fast rotation. These results can be readily demonstrated in experiments using the same configuration as in Phys. Rev.Lett. 122 110404(2019).  相似文献   

11.
Observing the CKM matrix elements written in different parametrization schemes,one can notice obvious relations among the sine-values of the CP phases in those schemes.Using the relations,we establish a few parametrizationindependent equations,by which the matrix elements of the CKM matrix can be completely fixed up to a universal parameter.If it is true,we expect that there should exist a hidden symmetry in the nature,which determines the relations.Moreover,it requires a universal parameter,naturally it would be the famous Jarlskog invariant,which is also parametrization independent.Thus the four parameters(three mixing angles and one CP phase) of the CKM matrix are not free,but determined by the symmetry and the universal parameter.As we generalize the rules to the PMNS matrix for neutrino mixing,the CP phase of the lepton sector is predicted to be within a range of 0 ~ 59° centered at39°(in the P_a parametrization) which will be tested in the future experiments.  相似文献   

12.
LIU Chun 《理论物理通讯》2007,47(6):1088-1098
It is proposed that supersymmetry (SUSY) may be used to understand fermion mass hierarchies. A family symmetry ZSL is introduced, which is the cyclic symmetry among the three generation SU(2) doublets. SUSY breaks at a high energy scale - 10^11 GeV. The electroweak energy scale- 100 GeV is unnaturally small No additional global symmetry, like the R-parlty, is imposed. The Yukawa couplings and R-parity violating couplings all take their natural values, which are О(10^0 -10^-2). Under the family symmetry, only the third generation charged ferrnions get their masses. This family symmetry is broken in the soft SUSY breaking terms, which result in a hierarchical pattern of the fermion masses. It turns out that for the charged leptons, the r mass is from the Higgs vacuum expectation value (VEV) and the sneutrino VEVs, the muon mass is due to the sneutrino VEVs, and the electron gains its mass due to both ZZL and SUSY hreaking. The large neutrino mixing are produced with neutralinos playing the partial role of right-handed neutrinos. │Ve3│, which is for Ve-Vr mixing, is expected to be about 0.1. For the quarks, the third generation masses are from the Higgs VEVs, the second generation masses are from quantum corrections, and the down quark mass due to the sneutrino VEVs. It explains me/ms, ms/me, md 〉 mu and so on. Other aspects of the model are discussed.  相似文献   

13.
The ground-state phase transition and the phonon dispersion relation of the quantum double-well model are studied by means of the time-dependent variational approach combined with a Hartree-type many-body trial wavefunction. The single-particle state is taken to be a frozen Jackiw-Kerman wavefunction. Under the condition of minimum uncertainty relation, we obtain an effective classical Hamiltonian for the system and equations of motion for the particle's expectation values. It is shown that the effective substrate potential transits from a symmetric double-well potential to a symmetric single-well potential, and the ground state exhibits a transition from a broken symmetry phase to a restored symmetry phase as increasing the strength of quantum fluctuations. We also obtain the phonon dispersion relations and the phonon gaps at the two phases.  相似文献   

14.
邢志忠 《中国物理 C》2012,36(2):101-105
The T2K Collaboration has recently reported a remarkable indication of the ν→ν oscillation which is consistent with a relatively large value of θ13 in the three-flavor neutrino mixing scheme. We show that it is possible to account for such a result of θ13 by introducing a natural perturbation to the democratic neutrino mixing pattern, without or with CP violation. A testable correlation between θ13 and θ23 is predicted in this ansatz. We also discuss the Wolfenstein-like parametrization of neutrino mixing, and comment on other possibilities of generating sufficiently large θ13 at the electroweak scale.  相似文献   

15.
In the framework of the canonical seesaw model,we present a simple but viable scenario to explicitly break an S_(3L)×S_(3R) flavor symmetry in the leptonic sector.It turns out that the leptonic flavor mixing matrix is completely determined by the mass ratios of the charged leptons(i.e.,me/mμand mμ/mτ) and those of light neutrinos(i.e.,m_1/m_2 and m_2/m_3).The latest global-fit results of the three neutrino mixing angles {θ_(12),θ_(13),θ_(23)}and two neutrino mass-squared differences {?m_(21)~2,?m_(31)~2} at the 3σ level are used to constrain the parameter space of {m_1/m_2,m_2/m_3}.The predictions for the mass spectrum and flavor mixing are highlighted:(1) the neutrino mass spectrum shows a hierarchical pattern and a normal ordering,e.g.,m_1≈2.2meV,m_2≈8.8 meV and m_3≈52.7 meV;(2) only the first octant of θ_(23) is allowed,namely,41.8? θ_(23) 43.3?;(3) the Dirac C P-violating phase δ≈-22?deviates significantly from the maximal value-90?.All these predictions are ready to be tested in ongoing and forthcoming neutrino oscillation experiments.Moreover,we demonstrate that the cosmological matter-antimatter asymmetry can be explained via resonant leptogenesis,including the individual lepton-flavor effects.In our scenario,leptonic C P violation at low-and high-energy scales is closely connected.  相似文献   

16.
We introduce a generalized concept of principal state of polarization (PSP) to analyse the piezoelectric polarization controller (PPC) and find each PPC unit can be described by a rotation matrix determined by the PSP. Our PPC has three components, each made of a jaw and a piezoelectric actuator with the squeezing direction tilted 0°, 45° and 0°, which are driven by a tunable power supply. We demonstrate that all the polarization rotation angles are linear to driving voltages and the PSP of unit 2 is nearly orthogonal to others which are almost equal. Taking some approximate treatments we obtain the matrix model of our PPC with respect to three driving voltages. The average error of our theoretical model is 1.51°, and the polarization response time is 〈50 μs, which is promising to realize an open-loop control of polarization.  相似文献   

17.
Symmetry breaking plays a pivotal role in modern physics.Although self-similarity is also a symmetry,and appears ubiquitously in nature,a fundamental question arises as to whether self-similarity breaking makes sense or not.Here,by identifying an important type of critical fluctuation,dubbed‘phases fluctuations’,and comparing the numerical results for those with self-similarity and those lacking self-similarity with respect to phases fluctuations,we show that self-similarity can indeed be broken,with significant consequences,at least in nonequilibrium situations.We find that the breaking of self-similarity results in new critical exponents,giving rise to a violation of the well-known finite-size scaling,or the less well-known finite-time scaling,and different leading exponents in either the ordered or the disordered phases of the paradigmatic Ising model on two-or three-dimensional finite lattices,when subject to the simplest nonequilibrium driving of linear heating or cooling through its critical point.This is in stark contrast to identical exponents and different amplitudes in usual critical phenomena.Our results demonstrate how surprising driven nonequilibrium critical phenomena can be.The application of this theory to other classical and quantum phase transitions is also anticipated.  相似文献   

18.
Hybrid density functional theory (DFT) calculations are performed to study MC2 (M= V, Cr, Fe and Co) clusters in the neutral and anionic charge states. We find that the equilibrium geometries of MC2 and their anions are all cyclic structures with C2v symmetry, which agrees well with the previous theoretical studies. The Mulliken charge and spin populations of MC2 clusters and their anions are also calculated, and it is found that the electron charge transformations from anions to neutral molecules mainly take place on the M atoms. Time-dependent DFT is used to calculate the excited states, and a theoretical assignment for the features in the experimental photoelectron spectrum is given, which are in good agreement with the available experimental data.  相似文献   

19.
We study the magneto-optical conductivity of a number of van der Waals heterostructures, namely, twisted bilayer graphene, AB–AB and AB–BA stacked twisted double bilayer graphene and monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride. As the magnetic field increases, the absorption spectrum exhibits a self-similar recursive pattern reflecting the fractal nature of the energy spectrum. Whilst twisted bilayer graphene displays only weak circular dichroism, the other four structures display strong circular dichroism with monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride being particularly pronounced owing to strong inversion symmetry breaking properties of the hexagonal boron nitride layer. As the left and right circularly polarized light interact with these structures differently, plane-polarized incident light undergoes a Faraday rotation and gains an ellipticity when transmitted. The size of the respective angles is on the order of a degree.  相似文献   

20.
We extend the T violating model of the paper on "Hidden symmetry of the CKM and neutrino mapping matrices" by assuming its T-violating phases X↑ and X↓ to be large and the same,with X = X↑= X↓.In this case,the model has 9 real parameters:α↑,β↑T,ξ↑,η↑ for the ↑-quark sector,α↑,β↑T,ξ↑,η↑ for the ↓sector and a common X.We examine whether these nine parameters are compatible with ten observables:the six quark masses and the four real parameters that characterize the CKM matrix (i.e.,the Jarlskog invariant J and three Eulerian angles).We find that this is possible only if the T violating phase X is large,between -120° to -135°.In this strong T violating model,the smallness of the Jarlskog invariant J ≌ 3 × 10-5 is mainly accounted for by the large heavy quark masses,with mc/mt< ms/mb≈ 0.02,as well as the near complete overlap of t and b quark,with (c|b)=-0.04.  相似文献   

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