禁闭弱作用亚夸克大统一理论

本文讨论了禁闭弱作用亚夸克大统一模型. 在合理的统一能标和禁闭标度条件下, 利用重整化群方法得到超色规范群SU(n)满足n≤3, 大统一规范群是SU(7). SU(8)和SO(14).     

大统一对手征前子模型的限制

本文由WNW条件^[1]出发,分析了大统一对禁闭弱作用手征前子模型的限制.我们发现超色群不能是SU(N)群及SO(M)群,而半单群SU(N)×SO(M)及SU(N)×SU(M)作为超色群是可行的.通过重整化群计算,得到在合理的能标10^{14GeV≤Λ_u≤1019GeV及300GeV≤Λ_MC≤1TeV下,可能的候选者是:G_MC=SU(3)×SO(5)及G_U≥SU(11);G_MC=SU(3)×SU(2)及G_U≥SU(12).}     

Rb(62D)原子与基态Rb原子,H2分子碰撞转移截面

本文用荧光法测量Rb(6²D)原子与基态Rb原子,H₂分子碰撞转移截面。结果表明:Rb(6²D)-Rb(5²s)转移截面为σ_fs=67×10^-14cm²,σ_tr=4.3×10^-14cm²,Rb(6²D)—H₂转移截面为σ_fs 关键词：     

分立对称性与SO(2n)大统一模型

本文应用分立对称性S, 对SO(2n)×S大统一模型进行了系统的分析. 我们的结论是: SO(14)×S与SO(16)×S是比较好的代大统一规范群. 作为例子, 本文给出SO(14)×S与SO(16)×S两个代大统一模型. 它们容纳了四代通常费米子, 并保持SU(3)_c渐近自由. 模型保留了SO(10)模型中得到的全部好的结果.     

格点规范场论Monte Carlo模拟中一种节省时间的取样方法

我们在格点规范场理论的Monte Carlo模拟中引入了一种节省时间的取样方法,研究了该方法在Z₂规范群和SU(3)规范群临界点附近的行为,发现在越过一阶相变点时该方法将失效。按一定的程序,此特点可用来寻找一阶相变点。     

SU(10)手征亚夸克大统一模型

本文在一些条件的限制下,讨论了SU(N)手征亚夸克大统一模型,结果要求10≤N≤19。并具体地构造了一个最小的SU(10)手征亚夸克大统一模型,预言了五代夸克和轻子的存在。 关键词：     

满足互补原理的SO(10)×SU(4)手征前子模型

本文反MAC (Most Attractive Channel)规则推广到半单超色规范群情形,构造了满足互补原理的SO(10)×SU(4)手征前子模型.该模型给出唯一解,预言了4代夸克和轻子,没有例外粒子出现.本文引入了代规范群SU(2)_g讨论了不同代费米子质量简并性的破缺.     

Same-sign tetralepton signature in type-Ⅱ seesaw at lepton colliders

The same-sign tetralepton signature via the mixing of neutral Higgs bosons and their cascade decays to charged Higgs bosons is a unique signal in the type-Ⅱ seesaw model with the mass spectrum M_A⁰≈M_H⁰>M_H⁺>M_H^±±.In this study,we investigate this signature at future lepton colliders,such as the ILC,CLIC,and MuC.Direct searches for doubly charged scalar H^±±at the LHC have excluded MHg+t<350(870) GeV in the H^±±+W^±W(±)(l^±±)decay mode.Therefore,we choose M_A⁰=400,600,1000,1500 GeV as our benchmark scenarios.Constrained by direct search,H^±±+W^±W(±)(l^±±)d=is the only viable decay mode for Mρ=400 GeV at the √s=1 TeV ILC.With an integrated luminosity L=8 ab^-1,the promising region,with approximately 150 signal events,corresponds to a narrow band in the range of 10^-4 GeV≤v△≤10^-2GeV.Meanwhile,for Mpo=600 GeV at the √s=1.5 TeV CLIC,approximately 10 signal events can be produced with L=2.5 ab^-1.For heavier triplet scalars M_A⁰■870 GeV,although the H^±± decay mode is allowed,the cascade decays are suppressed.A maximum event number~16 can be obtained at approximately v△~4×10⁴GeV and λ₁₄~0.26 for M_A⁰=1000 GeV with L=5 ab^-1 at the √s=3 TeV CLIC.Finally,we find that this signature is not promising for M_A⁰= 1500 GeV at the √s=6 TeV MuC.Based on the benchmark scenarios,we also study the observability of this signature.In the H^±±+W^±W(±)(l^±±)d mode,one can probe MρS 800(1160) GeV at future lepton colliders.     

在BaF2-BiF3系统中的相组成和离子电导

用固相反应法、X射线粉末衍射技术和复平面阻抗谱测量研究了BaF₂-BiF₃系统的相组成和离子电导。在此系统中发现了两种类型的Ba_1-xBi_xF_2+x固溶体:萤石型(0s≈0.5(14^1/2)a_F,c_{s< 关键词：}     

SU(4)磁单极子与双子解

以SU(4)规范群为例,提出一个简单求解磁单极子及双子的经典解的方法,它可系统地推广于一般的SU(N)群的情况.所得到的SU(4)单磁荷为■     

Low-energy predictions from grand unified theories

A theoretical framework to compute low-energy processes in a spontaneously broken gauge theory is devised. It applies in any gauge and uses conventional renormalisation schemes. Application of the method to SU(5) gives a range for M_X of 4.10¹³ GeV < M_X < 1.3 · 10¹⁵ GeV with a best value of 6.6 · 10¹⁴ GeV.     

Low-energy parity restoration and unification mass scale within maximal symmetries

We investigate the hierarchy of gauge boson masses in the maximal grand unified theory by studying the renormalization group equations for the running coupling constants associated with the symmetry breaking of SU(16)viaSU(12) _q×SU(4) _l×U(1) _|B|?|L| chain. Particular attention is given to the contribution of Higgs scalars to these equations. It is found that the intermediate mass scale M_L, associated with right-handed gauge bosons could be as low as 10 ³ GeV only for sin ²θ _w(M _L) as high as 0.265 with α _s(M _L)=0.13. In this chain of symmetry breaking, we have also examined the lowest unification mass that is allowed by the low-energy data for sin ²θ _w(M _L) and the assumed gauge hierarchy. This has been done in two cases; first for the case where SU(3) ^c is vectorial, second, for the case where SU(3) ^c is axial. In both cases the lowest unification mass scales were found to be 10 ¹³, 10 ¹¹, 10 ⁸ and 10 ⁷ GeV for sin ²θ _w(M _L) = 0.22, 0.24, 0.26,and0.265 respectively with α _s(M _L) = 0.13. The implication of these low unification masses on baryon non-conserving processes is also discussed.     

Phase transitions and magnetic monopoles in SO(10)

In a unified gauge theory based on SO(10), the combination of a strongly first order phase transition and a magnetic confinement mechanism can suppress the density of magnetic monopoles at the time of nucleosynthesis. However, this only occurs if SO(10) breaks down to SU(3)_c ? U (1)_em via SU(4)_c ? [SU(2)_L × SU(2)_R]. For the other symmetry breaking patterns of SO(10) obtained with a minimal Higgs system, the potential conflict with the standard big bang cosmology is not naturally avoided.     

Early unification and the Weinberg angle in the SU(4)4 grand unified model

In the framework of the grand unified gauge group SU(4)⁴ we discuss possibilities to reconcile the low unification scale (10⁵?10⁷ GeV) with the acceptable value of sin²θ_w. We consider various specific models which differ by the values of the intermediate mass scale, the choice of the fermion multiplets and by the embedding of the electroweak group SU(2) into SU(4)⁴. The class of theories with early unification and correct sin²θ_w is constructed. They all predict new non-sequential fermions which are SU(2)_L,R singlets and have unconventional electric charges. Cosmological implications of such theories are discussed and it is argued that new particles may well account for the positive results of searches for fractional charge in terrestrial matter.     

Towards a finite N = 2 susy GUT

We consider finite, N = 2 supersymmetric GUTs based on gauge groups SU(n) and SO(n). As an example, we discuss a semirealistic model based on SO(12). We argue that in finite, N = 2 supersymmetric GUTs, gauge symmetry breaking should occur dynamically. We present a heuristic picture in which this is induced by soft, finiteness preserving SUSY breaking terms. The bound states formed cause a very rapid evolution of the SO(12) coupling constant and break SO(12) into SU(4)×SU(3)_C×U(1).     

The price of natural flavour conservation in neutral weak interactions

The natural conservation of flavours to O(G_F²) in neutral weak interactions severely constrains choices of gauge groups as well as their fermion representations. In the absence of exactly conserved quantum numbers other than charge, and of |ΔQ| ? 2 charged currents, essentially the only weak and electromagnetic gauge groups whose neutral interactions naturally conserve all flavours are SU(2)_L ? U(1) and SU(2)_L ? [U(1)]². The plausible extensions of these gauge groups to grand unified models including the strong interactions are based on SU(5) and SO(10) respectively. Making the SU(5) model completely natural, including in the Higgs sector, gives the prediction $\text{m}{}_{\mathrm{<mtext>d</mtext>}}\text{/m}{}_{\mathrm{<mtext>e</mtext>}}\text{? m}{}_{\mathrm{<mtext>s</mtext>}}\text{/m}{}_{\mathrm{\mu }}\text{? m}{}_{\mathrm{<mtext>b</mtext>}}\text{/m}{}_{\mathrm{\tau }}\text{? 2605}$ where τ is the probable new heavy lepton and b is the conjectured third flavour of charge $\text{?1}\text{3}\text{quark}$. The SO(10) model contains a potential SU(2)_L ? SU(2)_R ? U(1) weak and electromagnetic gauge group, and has a complicated Higgs structure which does not naturally conserve quark flavours.     

Fermion spectra from superstrings

Some compactifications of the ten-dimensional anomaly-free E₈ × E₈ and SO(32) theories that correspond to superstrings are studied. Compactification is achieved by setting the classical gauge field equal to the spin connection. The resulting chiral fermion spectra are obtained for any six-dimensional manifold, under the condition Tr F² = 30 Tr R², plus a quantization condition for U(1) charges. For E₈ × E₈ these conditions lead to potentially realistic models for any irreducible six-dimensional manifold and any embedding of the holonomy group. Apart from a few more exotic examples, the four-dimensional models we obtain are more or less standard SU(5), SO(10), SU(4) × SU(2) × SU(2) or E₆ models.     

On the fermion spectrum of spontaneously generated fuzzy extra dimensions with fluxes

We consider certain vacua of four‐dimensional SU(N) gauge theory with the same field content as the 𝒩 = 4 supersymmetric Yang‐Mills theory, resulting from potentials which break the 𝒩 = 4 supersymmetry as well as its global SO(6) symmetry down to SO(3) × SO(3). We show that the theory behaves at intermediate scales as Yang‐Mills theory on M⁴ × S_L² × S_R², where the extra dimensions are fuzzy spheres with magnetic fluxes. We determine in particular the structure of the zero modes due to the fluxes, which leads to low‐energy mirror models.     

Bounds on the number and masses of quarks and leptons

We assume weak, electromagnetic and strong interactions to be asymptotically divergent, and to become strong at very large energies, of the order of the Plank mass. In this picture, the “low-energy” couplings (i.e. in the 10² GeV region) must be near the infrared stable point, and this allows us to put bounds on the number of elementary fermions (quarks and leptons). Similar assumptions on the Higgs couplings give bound on the fermion and on the Higgs boson masses. We consider the cases where weak and electromagnetic interactions are described by the gauge groups SU(2) ? U(1) or SU(2)_R ? U(1). The weak neutral current mixing angle is computed in both cases.     

ASO (10) model with Majorana masses for the vr's around 1011 GeV

A unified gauge model is built with Higgs in 210⊙126⊙10 representations and intermediate symmetry $$SU(3)_c \otimes SU(2)_L \otimes SU(2)_R \otimes U(1)_{B - L} .$$ . The vacuum of the210 is in a two-dimensional stratum. From the values sin²θ _W (M _W ) and \(\frac{\alpha }{{\alpha _s }}(M_W )\) one determines the high scales, with the result to predict leptoquarks heavier than 10¹⁵ GeV and Majorana masses for the right-handed neutrinos around 10¹¹ GeV.