Simple SO(10) Higgs models with the adjoint representation triggering the grand-unified symmetry breaking, discarded a long ago due to inherent tree-level tachyonic instabilities in the physically interesting scenarios, have been recently brought back to life by quantum effects. In this work we focus on the variant with 45_H+126_H in the Higgs sector and show that there are several regions in the parameter space of this model that can support stable unifying configurations with the B-L breaking scale as high as 10^14 GeV, well above the previous generic estimates based on the minimal survival hypothesis. This admits for a renormalizable implementation of the canonical seesaw and makes the simplest potentially realistic scenario of this kind a good candidate for a minimal SO(10) grand unification. Last, but not least, this setting is likely to be extensively testable at future large-volume facilities such as Hyper-Kamiokande.
We study the nature of the see-saw mechanism in the context of renormalizable SO(10) with Higgs fields in the 10-plets and 126-plet representations, paying special attention to the supersymmetric case. We discuss analytically the situation for the second and third generations of fermions ignoring any CP violating phase. It is shown that b-tau unification and large atmospheric mixing angle strongly disfavor the dominance of the type I see-saw.
Alternative renormalizable minimal non-SUSY SO(10) GUT model is proposed. Instead of a ${\bf 126}$-dimensional Higgs field, a ${\bf 120}$-dimensional Higgs filed is ntroducedin addition to a ${\bf 10}$-dimensional Higgs field and plays a crucial role to reproduce the realistic charged fermion mass matrices. With contributions of ${\bf 120}$ Higgs field, the original Witten's scenario of inducing the right-handed Majorana neutrino mass through 2-loop diagrams becomes phenomenologically viable. This model inherits the nice features of the conventional renormalizable minimal SO(10) GUT model with…
We address the problem of rationalizing the pattern of fermion masses and mixings by adding a nonabelian flavor symmetry in a grand unified framework. With this purpose, we include an A4 flavor symmetry into a unified renormalizable SUSY GUT SU(5) model. With the help of the "Type II Seesaw" mechanism we are able to obtain the pattern of observed neutrino mixings in a natural way, through the so called tribimaximal matrix.
We analyze all possible extensions of the recently proposed minimal renormalizable SUSY SU(5) grand unified model with the inclusion of an additional A4 flavor symmetry. We find that there are five possible cases but only one of them is phenomenologically interesting. We develop in detail such case and we show how the fermion masses and mixing angles come out. As a prediction we obtain the neutrino masses of order of 0.1 eV with an inverted hierarchy.
We propose a low scale renormalizable left-right symmetric theory that successfully explains the observed SM fermion mass hierarchy, the tiny values for the light active neutrino masses and is consistent with the lepton and baryon asymmetries of the Universe, the muon and electron anomalous magnetic moments as well as the with the constraints arising from the meson oscillations. In the proposed model the top and exotic quarks obtain masses at tree level, whereas the masses of the bottom, charm and strange quarks, tau and muon leptons are generated from a tree level Universal Seesaw mechanism, …
The hypothetical dark photon portal connecting the visible and dark sectors of the Universe has received considerable attention in recent years, with a focus on CP-conserving kinetic mixing between the Standard Model (SM) hypercharge gauge boson and a new U(1)$_X$ gauge boson. In the effective field theory context, one may write down non-renormalizable CP-violating kinetic mixing interactions involving the $X$ and SU(2)$_L$ gauge bosons. We construct for the first time a renormalizable model for CP-violating kinetic mixing that induces CP-violating non-Abelian kinetic mixing at mass dimension …
We develop a model of sneutrino inflation that is charged under $U(1)_{B-L}$ gauge symmetry in no-scale supergravity framework. The model provides an interesting modification of tribrid inflation. We impose $U(1)_R$ symmetry on the renormalizable level while allow Planck suppressed non-renormalizable operators that break R-symmetry. This plays a crucial role in realizing a Starobinsly-like inflation scenario from one hand. On the other hand it plays essential role, as well as SUSY breaking effects, in deriving the neutrino masses from TeV inverse seesaw mechanism. Thus we provide an interpreta…
Supersymmetric SO(10) grand unified models with renormalizable Yukawa couplings involving {\bf 10}, {\bf 126} and {\bf 120} Higgs fields have been shown to give a very economical theory for understanding quark-lepton flavor in a unified framework. In previous papers, we showed how nucleon decay can be suppressed in these models without invoking cancellation, by choice of Yukawa flavor texture within a type II seesaw framework for neutrinos that explains all mixings and masses including the recently observed "large" $θ_{13}$. In this follow-up paper, we extend our earlier work to the case of ty…
A realistic grand unified model has never been constructed in the literature due to three major difficulties: the seesaw mechanism without spoiling gauge coupling unification, the doublet-triplet splitting and the proton decay suppression. We propose a renormalizable supersymmetric SO(10) model with all these difficulties solved naturally by imposing an extra discrete symmetry.
The right--handed neutrino mass matrix that is central to the understanding of small neutrino masses via the seesaw mechanism can arise either (i) from renormalizable operators or (ii) from nonrenormalizable or super-renormalizable operators, depending on the symmetries and the Higgs content of the theory beyond the Standard Model. In this paper, we study lepton flavor violating (LFV) effects in the first class of seesaw models wherein the ν_R Majorana masses arise from renormalizable Yukawa couplings involving a B-L = 2 Higgs field. We present detailed predictions for τ-> μ+ γand μ-> e + γbra…
$SO(11)$ gauge-Higgs grand unification is formulated in the six-dimensional hybrid warped space in which the fifth and sixth dimensions play as the electroweak and grand-unification dimensions. Fermions are introduced in ${\bf 32}$, ${\bf 11}$ and ${\bf 1}$ of $SO(11)$. Small neutrino masses naturally emerge as a result of a new seesaw mechanism in the gauge-Higgs unification which is characterized by a $3 \times 3$ mass matrix.
We propose a grand unified SU(5)$\times$U(1)$_X$ model, where the standard SU(5) grand unified theory is supplemented by minimal seesaw and a right-handed neutrino dark matter with an introduction of a global $Z_2$-parity. In the presence of three right-handed neutrinos (RHNs), the model is free from all gauge and mixed-gravitational anomalies. The SU(5) symmetry is broken into the Standard Model (SM) gauge group at $M_{\rm GUT} \simeq 4 \times 10^{16}$ GeV in the standard manner, while the U(1)$_X$ symmetry breaking occurs at the TeV scale, which generates the TeV-scale mass of the U(1)$_X$ g…
The minimal SUSY SO(10) GUT models with {\bf 10}, {\bf 126} and {\bf 210} Higgs and only renormalizable couplings has been shown to provide a simple way to understand the neutrino mixings as well as the ratio $Δm^2_\odot/Δm^2_A$ in terms of quark mixing parameter $θ_{Cabibbo}$, provided neutrino masses are described by type II seesaw formula. However, in this minimal picture, it is impossible to realize type II dominance with renormalizable couplings in 4-dimensions. We show that this problem can be cured by embedding this model into a warped 5-dimensional space time with warping between the P…
We discuss a two scalar doublets model which induces the Higgs mechanism by means of a seesaw mechanism. This model naturally predicts a light Higgs scalar whose mass is suppressed by the grand unification scale. The model predicts an intermediate scale between the electroweak symmetry breaking scale and the grand unification scale at $10^9$ GeV. Below this intermediate energy scale the usual standard model appears as an effective theory. A seesaw mechanism in the scalar sector of the model not only induces the standard Higgs mechanism, but also solves the hierarchy problem. An implementation …
I present two new renormalizable grand unified theories where the neutrino masses are generated through the type I and type III seesaw mechanisms. These theories can be considered as the simplest (SUSY) renormalizable grand unified theories based on the SU(5) gauge symmetry. Several phenomenological and cosmological aspects of these proposals are discussed.
We revisit minimal non-supersymmetric models of SU(5) Grand Unification with the type II seesaw mechanism as the origin of neutrino masses. Imposing the requirement of gauge coupling unification and the proton lifetime bounds, we perform a Bayesian fit and obtain robust quantitative information on the mass scales of the beyond the Standard Model particles. We then study lepton-flavour-violating (LFV) processes induced by the type II scalar triplet and its SU(5) partners, showing that the interplay of upcoming searches for different LFV observables can provide additional information on the mass…
We investigate the possibility to find the simplest renormalizable grand unified theory based on the SU(5) gauge symmetry. We find that it is possible to generate all fermion masses with only two Higgs bosons, 5_H and 45_H. In this context the neutrino masses are generated through the type III and type I seesaw mechanisms. The predictions coming from the unification of gauge couplings and the stability of the proton are discussed in detail. In this theory the leptogenesis mechanism can be realized through the out of equilibrium decays of the fermions in the adjoint representation.
We present a Grand Unified model based on SO(10) with a Delta(27) family symmetry. Fermion masses and mixings are fitted and agree well with experimental values. An extended seesaw mechanism plays a key role in the generation of the leptonic mixing, which is approximately tri-bi-maximal.
An SO(10) grand unified model considered previously by the authors featuring lopsided down quark and charged lepton mass matrices is successfully predictive and requires that the lightest two right-handed Majorana neutrinons be nearly degenerate in order to obtain the LMA solar neutrino solution. Here we use this model to test its predictions for baryogenesis through resonant-enhanced leptogenesis. With the conventional type I seesaw mechanism, the best predictions for baryogenesis appear to fall a factor of three short of the observed value. However, with a proposed type III seesaw mechanism …
We investigate a scenario in a supersymmetric SO(10) Grand Unified Theory in which the fermion mass matrices are generated by renormalizable Yukawa couplings of the $\mathbf{10} \oplus \mathbf{120} \oplus \bar{\mathbf{126}}$ representation of scalars. We reduce the number of parameters by assuming spontaneous CP violation and a $\mathbbm{Z}_2$ family symmetry, leading to nine real Yukawa coupling constants for three families. Since in the ``minimal SUSY SO(10) GUT'' an intermediate seesaw scale is ruled out and our scenario lives in the natural extension of this theory by the $\mathbf{120}$, w…
We discuss in detail the symmetry breaking and related issues in the minimal renormalizable supersymmetric grand unified theory. We compute the particle spectrum and study its impact on the physical scales of the theory. This provides a framework for the analysis of phenomenological implications of the theory, to be carried out in part II.
We propose a new type of radiative seesaw model in which observed neutrino masses are generated through a three-loop level diagram in combination with tree-level type-II seesaw mechanism in a renormalizable theory. We introduce a Non-abelian flavor symmetry $T_7$ in order to constrain the form of Yukawa interactions and Higgs potential. Although several models based on a Non-abelian flavor symmetry predict the universal coupling constants among the standard model like Higgs boson and charged leptons, which is disfavored by the current LHC data, our model can avoid such a situation. We show a b…
Differently from the canonical seesaw mechanism, which is grounded in grand unified theories, the inverse seesaw mechanism lacks a special framework that realizes it naturally. In this work we advocate that the 3-3-1 model with right-handed neutrinos has such an appropriate framework to accommodate the inverse seesaw mechanism. We also provide an explanation for the smallness of the $μ$ parameter and estimate the branching ratio for the rare lepton flavor violation process $μ\rightarrow eγ$.
We consider fermion masses and mixings in a renormalizable SUSY SO(10) GUT with Yukawa couplings of scalar fields in the representation 10 + 120 + 126 bar. We investigate a scenario defined by the following assumptions: i) A single large scale in the theory, the GUT scale. ii) Small neutrino masses generated by the type I seesaw mechanism with negligible type II contributions. iii) A suitable form of spontaneous CP breaking which induces hermitian mass matrices for all fermion mass terms of the Dirac type. Our assumptions define an 18-parameter scenario for the fermion mass matrices for 18 exp…
A new supersymmetric grand unified model based on the gauge group $SU(5)\times SU(5)$ is discussed. The model has the feature that the conventional seesaw mechanism for neutrino masses is implemented using the $(15, 1)+(1,\bar{15)}$ representation. This multiplet may have a better chance of arising from level two compactification of superstring theories than the the ${bf \bar{126}}$ representation used in the SO(10) model. The model also naturally suppresses all R-parity violating interactions.
We study a class of models for tri-bimaximal neutrino mixing in SO(10) grand unified SUSY framework. Neutrino masses arise from both type-I and type-II seesaw mechanisms. We use dimension five operators in order to not spoil tri-bimaximal mixing by means of type-I contribution in the neutrino sector. We show that it is possible to fit all fermion masses and mixings including also the recent T2K result as deviation from the tri-bimaximal.
We show that the minimal renormalizable supersymmetric SO(10) GUT with the usual three generations of spinors has a Higgs sector consisting only of a "light" 10-dimensional and "heavy" 126, 126-bar and 210 supermultiplets. The theory has only two sets of Yukawa couplings with fifteen real parameters and ten real parameters in the Higgs superpotential. It accounts correctly for all the fermion masses and mixings. The theory predicts at low energies the MSSM with exact R-parity. It is arguably the minimal consistent supersymmetric grand unified theory.
We demonstrate that, for every grand unified model based on a conventional type I seesaw mechanism leading to a normal light neutrino mass hierarchy, one can easily generate a corresponding model with an inverted hierarchy which yields the same neutrino oscillation parameters. However, the latter type model has several unattractive instabilities which will disfavor any grand unified type I seesaw model, if an inverted neutrino mass hierarchy is observed experimentally. This should be contrasted with the softly-broken $L_e - L_μ- L_τ$ flavor symmetry models which are eliminated, if the data fav…
It is well known that a Weinberg dimension-5 operator for small neutrino masses can be realized at tree level in three types of renormalizable models: (i) the type-I seesaw mediated by fermion singlets, (ii) the type-II seesaw mediated by Higgs triplets, (iii) the type-III seesaw mediated by fermion triplets. We here point out such operator can be also induced at tree level by vector-like lepton doublets in association with unusual fermion singlets, Higgs triplets or fermion triplets. If these unusual fermion singlets, Higgs triplets or fermion triplets are heavy enough, their decays can gener…
We investigate the options for imposing flavor symmetries on a minimal renormalizable non-supersymmetric $\mathrm{SU}(5)$ grand unified theory, without introducing additional flavor-related fields. Such symmetries reduce the number of free parameters in the model and therefore lead to more predictive models. We consider the Yukawa sector of the Lagrangian, and search for all possible flavor symmetries. As a result, we find 25 distinct realistic flavor symmetry cases, with $\mathbb{Z}_2$, $\mathbb{Z}_3$, $\mathbb{Z}_4$, and $\mathrm{U}(1)$ symmetries, and no non-Abelian cases.
We briefly review the issues of proton decay and fermion masses and mixings in minimal supersymmetric grand unified theories. We argue that minimal SU(5), although tightly constrained by proton decay data, is still not ruled out. However, we outline the advantages of SO(10) unification, in particular in the model with renormalizable see-saw mechanism and its remarkable predictions of (a) exact R-parity at low energies, (b) large atmospheric neutrino angle as a consequence of b-tau unification and (c) 1-3 leptonic mixing angle close to its upper limit.
We extend the $SU(3)_c \times SU(2)_L \times U(1)_Y$ standard model by a $U(1)_{Y'}$ gauge symmetry. Three right-handed neutrinos are introduced to cancel the gauge anomaly. One Higgs singlet is responsible for spontaneously breaking the $U(1)_{Y'}$ symmetry while the standard model Higgs doublet does not carry any $U(1)_{Y'}$ charges. The down-type quarks, up-type quarks, charged leptons and neutral neutrinos obtain their Dirac masses through four types of dimension-5 operators constructed by the fermion doublets and singlets with the Higgs doublet and singlet. This effective theory is realiz…
Diverse mass and mixing patterns between the quarks and leptons makes it challenging to construct a simple grand unified theory of flavor. We show that SO(10) SUSY GUTs with type II seesaw mechanism giving neutrino masses provide a natural framework for addressing this issue. A simple ansatz that the dominant Yukawa matrix (the 10-Higgs coupling to matter) has rank one, appears to simultaneously explain both the large lepton mixings as well as the observed quark flavor hierarchy in these models. A testable prediction of this ansatz is the neutrino mixing, U_{e3}, which should be observable in …
We review the known ways of incorporating and breaking symmetries in a renormalizable way. We summarize the various grand unified theories based on $SU_5, SO_{10}$, and $E_6$ as family enlargement groups. An $SU_5$ model with an $SU_2$ gauged family group is presented as an illustration. In it, the e-family (i.e., e,u and d) is classically massless and acquires calculable mass corrections. The family group is broken by the same agent that does the superstrong breaking. Finally, we sketch a way of unifying the family group with $SU_5$ into $SU_8$.
A non-minimal, semi-realistic version of supersymmetric SU(5) grand unified theory is discussed. The solution of the doublet-triplet splitting problem leads to a better agreement between the predicted and observed values of the low-energy strong coupling constant and to a prolongation of the proton lifetime. A U(1) flavor symmetry allows to accommodate a realistic mass spectrum in the charged and in the neutral fermion sectors and protects doublet-triplet splitting and proton decay from dangerous radiative corrections or non-renormalizable operators.
We comment on the status and prospects of the minimal non-supersymmetric renormalizable SO(10) grand unified model. We emphasize its unique predictive power owing to the particular robustness of the gauge unification pattern to the leading-order Planck-scale effects which, in turn, makes it essentially the only unified framework in which the proton lifetime may be estimated with better than the leading order precision. This, together with the frequent presence of light-scale exotics accessible, in principle, at future colliders, is the key to its potential testability at the upcoming megaton-s…
We investigate the conditions on the Higgs sector that allow supersymmetric SO(10) grand unified theories (GUT) to break spontaneously to the standard electroweak model (SM) at the renormalizable level. If one considers Higgs representations of dimension up to the adjoint, a supersymmetric standard model vacuum requires in most cases the presence of non-renormalizable (NR) operators. The active role of Planck induced NR operators in the breaking of the gauge symmetry introduces a hierarchy in the mass spectrum at the GUT scale that may be an issue for gauge unification and proton decay. We sho…
Seesaw mechanism appears to be the simplest and most appealing way to understand small neutrino masses observed in recent experiments. It introduces three right handed neutrinos with heavy masses to the standard model, with at least one mass required by data to be close to the scale of conventional grand unified theories. This may be a hint that the new physics scale implied by neutrino masses and grand unification of forces are one and the same. Taking this point of view seriously, I explore different ways to resolve the puzzle of large neutrino mixings in grand unified theories such as SO(10…
In the left-right symmetric models, we can take the left-right symmetry to be the charge-conjugation and then impose a global symmetry under which the left- and right-handed fermion doublets carry equal but opposite charges. Consequently, we may introduce two Higgs bi-doublets to give the desired fermion mass spectrum. The global symmetry is identified to a Peccei-Quinn symmetry. We can introduce a complex scalar singlet to break the global Peccei-Quinn symmetry at a high scale. This symmetry breaking is also responsible for generating the heavy Majorana masses of the fermion singlets which ha…
We propose a renormalizable multi-Higgs model with $A_{4}\otimes Z_{2}\otimes Z^{\prime}_{2}$ symmetry, accounting for the experimental deviation from the tribimaximal mixing pattern of the neutrino mixing matrix. In this framework we study the charged lepton and neutrino masses and mixings. The light neutrino masses are generated via a radiative seesaw mechanism, which involves a single heavy Majorana neutrino and neutral scalars running in the loops. The obtained neutrino mixings and mass squared splittings are in good agreement with the neutrino oscillation experimental data for both normal…
The measure of the triple Higgs coupling is one of the major goals of the high-luminosity run of the CERN Large Hadron Collider (HL-LHC) as well as the future colliders, either leptonic such as the International Linear Collider (ILC) or hadronic such as the 100 TeV Future Circular Collider in hadron-hadron mode (FCC-hh). We have recently proposed this observable as a test of neutrino mass generating mechanisms in a regime where heavy sterile neutrino masses are hard to be probed otherwise. We present in this article a study of the one-loop corrected triple Higgs coupling in the inverse seesaw …
I review a recent work on gauged flavor with left-right symmetry, where all masses and all Yukawa couplings owe their origin to spontaneous flavor symmetry breaking. This is suggested as a precursor to a full understanding of flavor of quarks and leptons. An essential ingredient of this approach is the existence of heavy vector-like fermions, which is the home of flavor, which subsequently gets transmitted to the familiar quarks and leptons via the seesaw mechanism. I then discuss implications of extending this idea to include supersymmetry and finally speculate on a possible grand unified mod…
Alternatives to the traditional grand unified theory seesaw for neutrino masses are briefly described. These include the possibility of large extra dimensions and various possibilities for models involving an extra U(1)' gauge symmetry. The difficulty of observing Majorana phases in neutrinoless double beta decay is also briefly commented on.
A simple extension of the minimal renormalizable supersymmetric SO(10) grand unified theory by adding a 120-dimensional Higgs representation is examined. This brings new antisymmetric contributions to the relevant quark and lepton mass sum rules and leads to a better fit of the measured values of lepton masses and mixings together with a natural completion of the renormalizable Higgs sector within the SUSY SO(10) framework.
A set of Grand Unified Theories based upon the gauge groups $SU(5)_Ł\times SU(5)_\R$, $SO(10)_Ł\times SO(10)_\R$ and $SU(4)_\C \times SU(4)_Ł\times SU(4)_\R$ is explored. Several novel features distinguish these theories from the well-known $SU(5)$, $SO(10)$ and $SU(4)_\C \times SU(2)_Ł\times SU(2)_\R$ models which they generalize. Firstly, Standard Model quarks and leptons are accompanied by and mix with heavy $SU(2)_Ł\times SU(2)_\R$ singlet partners. The resulting fermion mass matrices are seesaw in form. Discrete parity symmetries render the determinants of these mass matrices real and eli…
$SO(5) \times U(1) \times SU(3)$ gauge-Higgs unification model inspired by $SO(11)$ gauge-Higgs grand unification is constructed in the Randall-Sundrum warped space. The 4D Higgs boson is identified with the Aharonov-Bohm phase in the fifth dimension. Fermion multiplets are introduced in the bulk in the spinor, vector and singlet representations of $SO(5)$ such that they are implemented in the spinor and vector representations of $SO(11)$. The mass spectrum of quarks and leptons in three generations is reproduced except for the down quark mass. The small neutrino masses are explained by the ga…
We present a detailed study of the quark and lepton mass spectra in a SO(10) framework with one 10_H and one \bar{126}_H Higgs representations in the Yukawa sector. We consider in full generality the interplay between type-I and type-II seesaws for neutrino masses. We first perform a χ^2 fit of fermion masses independent on the detailed structure of the GUT Higgs potential and determine the regions in the parameter space that are preferred by the fermion mass sum rules. We then apply our study to the case of the minimal renormalizable SUSY SO(10) GUT with one 10_H, one \bar{126}_H, one 126_H, …
We investigate the role of CP phases within the renormalizable SUSY SO(10) GUT with one 10_H, one 126bar_H one 126_H and one 210_H Higgs representations and type II seesaw dominating the neutrino mass matrix. This framework is non trivially predictive in the fermionic sector and connects in a natural way the GUT unification of b and tau Yukawa couplings with the bi-large mixing scenario for neutrinos. On the other hand, existing numerical analysis claim that consistency with quark and charged lepton data prevents the minimal setup from reproducing the observed CP violation via the Cabibbo-Koba…
We present a new possibility for achieving doublet-triplet splitting naturally in supersymmetric SO(10) grand unified theories. It is based on a missing partner mechanism which is realized with the 126 + 126-bar Higgs superfields. These Higgs fields, which are also needed for generating Majorana right-handed neutrino masses, contain a pair of color triplets in excess of weak doublets. This feature enables us to remove the color triplets from the low energy spectrum without fine-tuning. We give all the needed ingredients for a successful implementation of the missing partner mechanism in SO(10)…
A predictive framework for fermion masses and mixing is given by the supersymmetric SO(10) model with one 10, one bar126, one 126 and one 210 Higgs representations, and type II seesaw dominating the neutrino mass matrix. We investigate the origin of the tension between this model and lepton mixing data and refine previous numerical analyses. We discuss an extension of the minimal model that includes one 120 Higgs chiral superfield representation. This exhausts the possible renormalizable contributions to the Yukawa sector. In spite of the increase in the number of parameters the predictivity o…
A realistic extension of the minimal $SU(5)$ theory consisting of the addition of an adjoint fermion is known to predict light real fermion and scalar weak triplets, potentially accessible at the LHC. These particles, in addition to playing a key role in gauge coupling unification, have profound phenomenological implications. The fermion triplet, that through the seesaw mechanism offers a testable origin of neutrino mass, has been already extensively discussed. The scalar triplet develops a vacuum expectation value that modifies the $W$-boson mass. We show that its low-energy effective theory …
In this talk, we introduce a new scenario of grand unified theory (GUT) with anomalous $U(1)_A$ gauge symmetry. Since generic interactions (including non-renormalizable interactions) are introduced, once we fix the symmetry of the theory, we can define the theory without O(1) coefficients. The number of parameters to determine the symmetry is just 11 or 12 integer parameters which are anomalous $U(1)_A$ charges(integer) for introduced multiplets. It is surprising that the GUT scenario can explain doublet-triplet splitting, quark and lepton masses and mixing angles. In neutrino sector, the scen…
We reconsider a class of well motivated supersymmetric models in which inflation is associated with the breaking of a gauge symmetry G to H, with the symmetry breaking scale M~10^16 GeV. Starting with a renormalizable superpotential, we include both radiative and supergravity corrections to derive the inflationary potential. The scalar spectral index n_s can exceed unity in some cases, and it cannot be smaller than 0.98 if the number of e-foldings corresponding to the present horizon scale is around 60. Two distinct variations of this scenario are discussed in which non-renormalizable terms al…
We examine how a scenario of coexisting two-particle dark mater can be realized in the extended seesaw model, which we have proposed previously to accommodate small neutrino masses and low scale leptogenesis with an introduction of singlet Majorana neutrino $S$ and singlet scalar $ϕ$. We now impose the discrete symmetry $Z_2 \times Z_2^{\prime}$ and introduce new renormalizable interaction terms with a new heavy singlet scalar particle $Φ$ so as for previously introduced $S$ and $ϕ$ to be doubly coexisting dark matter candidates. Depending on the mass spectrum of the two dark matter candidates…
The recent measurement of a non-zero neutrino mixing angle $θ_{13}$ requires a modification of the tri-bimaximal mixing pattern that predicts a zero value for it. We propose a new neutrino mixing pattern based on a spontaneously-broken $A_{4}$ flavor symmetry and a type-I seesaw mechanism. Our model allows for approximate tri-bimaximal mixing and non-zero $θ_{13}$, and contains a natural way to implement low and high energy CP violation in neutrino oscillations, and leptogenesis with a renormalizable Lagrangian. Both normal and inverted mass hierarchies are permitted within $3σ$ experimental b…
In this work we propose a renormalizable model based on the $SU(5)$ gauge group where neutrino mass originates at the two-loop level without extending the fermionic content of the Standard Model (SM). Unlike the conventional $SU(5)$ models, in this proposed scenario, neutrino mass is intertwined with the charged fermion masses. In addition to correctly reproducing the SM charged fermion masses and mixings, neutrino mass is generated at the quantum level, hence naturally explains the smallness of neutrino masses. In this set-up, we provide examples of gauge coupling unification that simultaneou…
