ترغب بنشر مسار تعليمي؟ اضغط هنا

Standard Model gauge couplings from gauge-dilatation symmetry breaking

141   0   0.0 ( 0 )
 نشر من قبل Kosuke Odagiri
 تاريخ النشر 2013
  مجال البحث
والبحث باللغة English
 تأليف Kosuke Odagiri




اسأل ChatGPT حول البحث

We argue that there is a spontaneously broken rotational symmetry between space-time coordinates and gauge theoretical phases. The dilatonic mode acts as the massive Higgs boson, whose vacuum expectation value determines the gauge couplings. This mechanism requires that the quadratic divergences, or tadpoles of the three gauge-theory couplings, unify at a certain scale. We verify this statement, and find that this occurs at Lambda_u ~ 4x10^7 GeV. The tadpole cancellation condition, together with the dilaton self-energy, fixes the value of the unified tadpole coefficient to be 1/[4 ln(Lambda_cut/Lambda_u)]. The observed values of the coupling constants at Lambda_u then implies Lambda_cut ~ 4x10^18 GeV, which is close to the value of the reduced Planck mass MR_Pl=M_Pl/sqrt(8 pi)=2.4 x 10^18 GeV. In other words, by assuming a cutoff at M_Pl or MR_Pl, we are able to obtain predictions for the gauge couplings which agree with the true values to within a few percent. It turns out that this symmetry breaking can only take place if mass is generated with the aid of some other means such as electroweak symmetry breaking. Assuming dynamical symmetry breaking originating at MR_Pl, we obtain M_chi ~ 10^9 GeV, which is not unreasonable but somewhat higher than Lambda_u. The cancellation of an anomaly in the dilaton self-energy requires that the number of fermionic generations equals three.



قيم البحث

اقرأ أيضاً

We discuss the local (gauged) Weyl symmetry and its spontaneous breaking and apply it to model building beyond the Standard Model (SM) and inflation. In models with non-minimal couplings of the scalar fields to the Ricci scalar, that are conformal in variant, the spontaneous generation by a scalar field(s) vev of a positive Newton constant demands a negative kinetic term for the scalar field, or vice-versa. This is naturally avoided in models with additional Weyl gauge symmetry. The Weyl gauge field $omega_mu$ couples to the scalar sector but not to the fermionic sector of a SM-like Lagrangian. The field $omega_mu$ undergoes a Stueckelberg mechanism and becomes massive after eating the (radial mode) would-be-Goldstone field (dilaton $rho$) in the scalar sector. Before the decoupling of $omega_mu$, the dilaton can act as UV regulator and maintain the Weyl symmetry at the {it quantum} level, with relevance for solving the hierarchy problem. After the decoupling of $omega_mu$, the scalar potential depends only on the remaining (angular variables) scalar fields, that can be the Higgs field, inflaton, etc. We show that successful inflation is then possible with one of these scalar fields identified as the inflaton. While our approach is derived in the Riemannian geometry with $omega_mu$ introduced to avoid ghosts, the natural framework is that of Weyl geometry which for the same matter spectrum is shown to generate the same Lagrangian, up to a total derivative.
We systematically search intersecting D-brane models, which just realize the Standard Model chiral matter contents and gauge symmetry. We construct new classes of non-supersymmetric Standard Model-like models. We also study gauge coupling constants o f these models. The tree level gauge coupling is a function of compactification moduli, string scale, string coupling and winding number of D-branes. By tuning them, we examine whether the models can explain the experimental values of gauge couplings. As a result, we find that the string scale should be greater than $10^{14-15}$GeV if the compactification scale and the string scale are the same order.
We study perturbations that break gauge symmetries in lattice gauge theories. As a paradigmatic model, we consider the three-dimensional Abelian-Higgs (AH) model with an N-component scalar field and a noncompact gauge field, which is invariant under U(1) gauge and SU(N) transformations. We consider gauge-symmetry breaking perturbations that are quadratic in the gauge field, such as a photon mass term, and determine their effect on the critical behavior of the gauge-invariant model, focusing mainly on the continuous transitions associated with the charged fixed point of the AH field theory. We discuss their relevance and compute the (gauge-dependent) exponents that parametrize the departure from the critical behavior (continuum limit) of the gauge-invariant model. We also address the critical behavior of lattice AH models with broken gauge symmetry, showing an effective enlargement of the global symmetry, from U(N) to O(2N), which reflects a peculiar cyclic renormalization-group flow in the space of the lattice AH parameters and of the photon mass.
115 - Koichi Yamawaki 2018
The Standard Model (SM) Higgs Lagrangian is straightforwardly rewritten into the {it scale-invariant} nonlinear sigma model $G/H=[SU(2)_L times SU(2)_R]/SU(2)_{V}simeq O(4)/O(3)$, with the (approximate) scale symmetry realized nonlinearly by the (pse udo) dilaton ($=$ SM Higgs). It is further gauge equivalent to that having the symmetry $O(4)_{rm global}times O(3)_{rm local}$, with $O(3)_{rm local}$ being the Hidden Local Symmetry (HLS). In the large $N$ limit of the scale-invariant version of the Grassmannian model $G/H=O(N)/[O(N-3)times O(3)] $ $simeq O(N)_{rm global}times [O(N-3)times O(3)]_{rm local}$, identical to the SM for $Nrightarrow 4$, we show that the kinetic term of the HLS gauge bosons (SM rho) $rho_mu$ of the $O(3)_{rm local}simeq [SU(2)_V]_{rm local}$ are dynamically generated by the nonperturbative dynamics of the SM itself. The dynamical SM rho stabilizes the skyrmion (SM skyrmion) $X_s$ as a dark matter candidate within the SM: The mass $M_{X_s} ={cal O}(10, {rm GeV})$ consistent with the direct search experiments implies the induced HLS gauge coupling $g_{_{rm HLS}}={cal O}(10^3)$, which realizes the relic abundance, $Omega_{X_s} h^2 ={cal O}(0.1)$. If instead $g_{_{rm HLS}}lesssim 3.5$ ($M_rho lesssim 1.2 $ TeV), the SM rho could be detected with narrow width $lesssim 100 ,{rm GeV}$ at LHC, having all the $a=2$ results of the generic HLS Lagrangian ${cal L}_A+ a {cal L}_V$, i.e., $rho$-universality, KSRF relations and the vector meson dominance, independently of $a$. There exists the second order phase phase transition to the unbroken phase having massless $rho_mu$ and massive $pi$ (no longer NG bosons), both becoming massless free particles just on the transition point (scale-invariant ultraviolet fixed point).The results readily apply to the 2-flavored QCD as well.
219 - Radovan Dermisek 2012
We discuss gauge coupling unification in models with additional 1 to 4 complete vector-like families, and derive simple rules for masses of vector-like fermions required for exact gauge coupling unification. These mass rules and the classification sc heme are generalized to an arbitrary extension of the standard model. We focus on scenarios with 3 or more vector-like families in which the values of gauge couplings at the electroweak scale are highly insensitive to the grand unification scale, the unified gauge coupling, and the masses of vector-like fermions. Their observed values can be mostly understood from infrared fixed point behavior. With respect to sensitivity to fundamental parameters, the model with 3 extra vector-like families stands out. It requires vector-like fermions with masses of order 1 TeV - 100 TeV, and thus at least part of the spectrum may be within the reach of the LHC. The constraints on proton lifetime can be easily satisfied in these models since the best motivated grand unification scale is at $sim 10^{16}$ GeV. The Higgs quartic coupling remains positive all the way to the grand unification scale, and thus the electroweak minimum of the Higgs potential is stable.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا