International Journal of Modern Physics A

Various proposals of electron and muon colliders have been put forward for precision studies of the Higgs properties. It is shown that in both cases of Higgs resonant production through a muon collider, and associated HZ production in a electron–positron collider sizeable QED radiative effects must be carefully taken into account for the precise measurements of the decay channels of the Higgs particle.

We investigate the effect of a black hole as a nucleation site of a false vacuum bubble based on the Euclidean actions of relevant configurations. As a result we find a wormhole-like configuration may be spontaneously nucleated once the black hole mass falls below a critical value of order of the Hubble parameter corresponding to the false vacuum energy density. As the space beyond the wormhole throat can expand exponentially, this may be interpreted as creation of another inflationary universe in the final stage of the black hole evaporation.

We briefly summarize some searches for Higgs bosons with a mass of $\lesssim 110$ GeV at LEP and the LHC. We discuss a possible signal in the diphoton decay mode at $m_{\varphi }\sim 96$ GeV as reported by CMS, together with a $\sim 2\sigma$ hint in the $b\bar{b}$ final state at LEP. We briefly review possible interpretation of such a new particle in various BSM models. We focus on possible explanations as reported within the NMSSM and the $\mu \nu$SSM. Conclusions for future collider projects are briefly outlined.

The breakdown of $E_6$ within the supersymmetric (SUSY) Grand Unified Theories (GUTs) can result in SUSY extensions of the standard model (SM) based on the SM gauge group together with extra $U(1)$ gauge symmetry under which right-handed neutrinos have zero charge. In these $U{(1)}_N$ extensions of the minimal supersymmetric standard model (MSSM) a single discrete ${\tilde{Z}}_2^H$ symmetry may be used to suppress the most dangerous operators, that give rise to proton decay as well as nondiagonal flavour transitions at low energies. The SUSY models under consideration involves $Z^{\prime }$ and extra exotic matter beyond the MSSM. We discuss leptogenesis within this SUSY model and argue that the extra exotic states may lead to the nonstandard Higgs decays.

We present two original derivations of the restoration of C and CP symmetry within QCD, simplest in “standalone QCD” but extendable to include conserved QED, in the limit

Recent analyses of modern cosmological data show that the $\mathrm{\Lambda }=\mathrm{\text{const}}$ hypothesis, despite being the canonical framework, might well not be the most favored one from the phenomenological point of view. A number of persisting tensions with the observations (particularly with the data on structure formation and the local measurements of the Hubble parameter) indicate that the concordance or $\mathrm{\Lambda }$CDM model of cosmology might be in trouble. The combined fit to SNIa+BAO+H(z)+LSS+BBN+CMB observables shows that the performance of the $\mathrm{\Lambda }$CDM is not as good as could be expected, and in fact it may lag behind the fitting outcome from dynamical dark energy (DDE) models. A simple XCDM parameterization seems to perform better than the $\mathrm{\Lambda }$CDM. Furthermore, the running vacuum model (RVM) could also be superior in fitting the overall data and in smoothing out some of the mentioned tensions.

The weak bosons are bound states. The state with the lowest mass is identified with the boson, which has been discovered at the LHC. The p-wave excitations are studied. Specific properties of the excited bosons are discussed, in particular their decays into weak bosons and photons. The stable fermion, consisting of three fermions, provides the dark matter in our universe.

We demonstrate that a phenomenologically viable four-dimensional grand unified theory with no proton decay can be constructed. This is done in the framework of the minimal nonsupersymmetric SU(5) GUT by introducing new representations and separating the physical quark and lepton fields into different multiplets. In such a theory all beyond Standard Model particles are naturally heavy, but one can tune the parameters of the model such that gauge coupling unification is achieved and some of the new particles are at the TeV scale and accessible at the LHC.

In this paper, I present the recently established hyperunified field theory (HUFT)${}^{1,2}$ for all basic forces and elementary particles within the framework of gravitational quantum field theory (GQFT)${}^{3,4}$ in hyper-space–time. GQFT treats gravity as a gauge theory in the framework of quantum field theory to avoid the long term obstacle between general relativity and quantum mechanics. HUFT is built based on the guiding principle: the dimension of hyper-space–time correlates to intrinsic quantum numbers of basic building blocks of nature, and the action describing the laws of nature obeys the gauge invariance and coordinate independence, which is more fundamental than that proposed by Einstein for general relativity. The basic gravitational field is defined in biframe hyper-space–time as a bicovariant vector field, it is a gauge-type hyper-gravifield rather than a metric field. HUFT is characterized by a bimaximal Poincaré and hyper-spin gauge symmetry $\mathrm{\text{PO}}(1,D_h-1)⨝\mathrm{\text{SP}}(1,D_h-1)$ with a global and local conformal scaling invariance in biframe hyper-space–time. The gravitational origin of gauge symmetry is revealed through the hyper-gravifield that plays an essential role as a Goldstone-like field, which enables us to demonstrate the gauge-gravity and gravity-geometry correspondences and to corroborate the gravitational gauge-geometry duality with an emergent hidden general linear group symmetry $\mathrm{\text{GL}}(D_h,R)$. The Taiji Program in Space for the gravitational wave detection in China${}^{5\text{–}7}$ is briefly outlined.

We analyze status of $C$, $P$ and $T$ discrete symmetries in application to neutron–antineutron transitions breaking conservation of baryon charge ${ℬ}$ by two units. At the level of free particles, all these symmetries are preserved. This includes $P$ reflection in spite of the opposite internal parities usually ascribed to neutron and antineutron. Explanation, which goes back to the 1937 papers by Majorana and Racah, is based on a definition of parity satisfying $P^2=-1$, instead of $P^2=1$, and ascribing $P=i$ to both, neutron and antineutron. We apply this to $C$, $P$ and $T$ classification of six-quark operators with $\left|\mathrm{\Delta }{ℬ}\right|=2$. It allows to specify operators contributing to neutron–antineutron oscillations. Remaining operators contribute to other $\left|\mathrm{\Delta }{ℬ}\right|=2$ processes and, in particular, to nuclei instability. We also show that presence of external magnetic field does not induce any new operator mixing the neutron and antineutron provided that rotational invariance is not broken.

The abundances of baryons and leptons are not only closely related to each other and to the generation of neutrino masses but may also be linked to the dark matter in the Universe. In this paper we review how a consistent physics beyond the Standard Model framework for cosmology and neutrino masses could arise by studying these interrelations.

We consider two realistic models for a scale invariant extension of the standard model, which couples with a hidden non-Abelian gauge sector. At energies around TeV, the hidden sector becomes strongly interacting, thereby generating a robust energy scale, which is transferred to the standard model sector, triggering the electroweak symmetry breaking. At a finite temperature, i.e. in the early Universe, the generation of the robust energy scale appears as a strong first-order phase transition. We calculate the gravitational wave background spectrum for both models, which is produced by the first-order phase transition. We compare the results with the experimental sensitivity of LISA and DECIGO and find the gravitational wave signal may be detected at DECIGO.

Recent proposals have suggested that a previously unknown decay mode of the neutron into a dark matter particle could solve the long lasting measurement problem of the neutron decay width. We show that, if the dark particle in neutron decay is the major component of the dark matter in the universe, this proposal is in disagreement with modern astrophysical data concerning neutron star masses.

I discuss a general class of models where the inflation is driven by supersymmetry breaking with the superpartner of the goldstino (sgoldstino) playing the role of the inflaton. Imposing an R-symmetry allows to satisfy easily the slow-roll conditions, avoiding the so-called $\eta$-problem, and leads to two different classes of small field inflation models; they are characterized by an inflationary plateau around the maximum of the scalar potential, where R-symmetry is either restored or spontaneously broken, with the inflaton rolling down to a minimum describing the present phase of our Universe. Inflation can be driven by either an F- or a D-term, while the minimum has a positive tunable vacuum energy. The models agree with cosmological observations and in the simplest case predict a tensor-to-scalar ratio of primordial perturbations $10^{-9}\lesssim r\lesssim 10^{-4}$ and an inflation scale $10^{10}\mathrm{\text{GeV}}\lesssim H_{\ast }\lesssim 10^{12}\mathrm{\text{GeV}}$.

This paper aims at showing how to probe gravity in a model independent way using observable quantities which can be measured with the minimum number of assumptions.

We find that it is possible to estimate the gravitational slip, defined as the ratio of the gravitational potentials, independently of assumptions concerning initial conditions, bias, and other cosmological parameters. Analyzing all the data currently available, we find $\eta \approx 0.5\pm 0.9$ in the redshift range $z=0.2\text{–}0.8$. Future datasets, like those provided by the Euclid satellite, will tighten this constraint by more than an order of magnitude.

Some problems of spontaneous and gravitational baryogenesis are discussed. Gravity modification due to the curvature-dependent term in gravitational baryogenesis scenario is considered. It is shown that the interaction of baryonic fields with the curvature scalar leads to strong instability of the gravitational equations of motion and as a result to noticeable distortion of the standard cosmology.

We consider the $A_4$, $S_4$ and $A_5$ discrete lepton flavor symmetries broken down to nontrivial residual symmetries in the charged lepton and neutrino sectors in such a way that at least one of them is a $Z_2$. Such symmetry breaking patterns lead to predictions for some of the three neutrino mixing angles and/or the Dirac CP violation phase $\delta$ of the neutrino mixing matrix. First, we perform a statistical analysis of these predictions, which uses as input the latest global data on the neutrino mixing parameters. We find 14 phenomenologically viable cases. Further, we assess the viability of these cases taking into account the prospective uncertainties in the determination of the mixing angles, planned to be achieved in current and future neutrino oscillation experiments. We find that only six cases would be compatible with the assumed prospective data. We show that this number will be further reduced by a precision measurement of $\delta$.

A new paradigm for black holes is introduced. It is known as the External Energy Paradigm. The paradigm asserts that all energies of a black hole are external quantities; they are absent inside the horizon. These energies include constituent mass, gravitational energy, electrostatic energy, rotational energy, heat energy, etc. As a result, quantum particles with charges and spins cannot exist inside the black hole. To validate the conclusion, we derive the moment of inertia of a Schwarzschild black hole and find that it is exactly equal to mass $\times$ (Schwarzschild radius)², indicating that all mass of the black hole is located at the horizon. This remarkable result can resolve several long-standing paradoxes in black hole theory; such as why entropy is proportional to area and not to volume, the singularity problem, the information loss problem and the perplexing firewall controversy.

Search for heavy neutral lepton (HNL) production in charged kaon decays using the data collected by kaon experiments NA48/2 and NA62 at CERN are reported. Upper limits are established on the elements of the extended neutrino mixing matrix for heavy neutral lepton mass in the range 130–450 MeV, improving on the results from previous HNL production search.

The spin-charge-family theory, which is a kind of the Kaluza–Klein theories in $d=(13+1)$ — but with the two kinds of the spin connection fields, the gauge fields of the two Clifford algebra objects, $S^{ab}$ and ${\tilde{S}}^{ab}$ — explains all the assumptions of the standard model: The origin of the charges of fermions appearing in one family, the origin and properties of the vector gauge fields of these charges, the origin and properties of the families of fermions, the origin of the scalar fields observed as the Higgs’s scalar and the Yukawa couplings. The theory explains several other phenomena like: The origin of the dark matter, of the matter–antimatter asymmetry, the “miraculous” triangle anomaly cancellation in the standard model and others. The more work is invested in this theory, the more explanations of the observed phenomena the theory is offering. Since the theory starts at $d\ge (13+1)$ with a simple action for bosons and fermions, with the fermions carrying only two kinds of spins and no charges and interacting only through gravity (the vielbeins and the two kinds of the spin connection fields) and with the gravity as the only boson fields, the questions arises not only how do the two kinds of spins of fermions in $d$ manifest the spin, charges and family quantum numbers in $(3+1)$, and how does the gravity in $d$ manifests as all the observed gauge fields, the scalar fields and the Yukawa couplings, offering also explanation for matter–antimatter asymmetry and the existing of the dark matter, but also why “nature makes a choice of the Clifford algebra rather than the Grassmann algebra” although both kinds of degrees of freedom enable anticommutation relations for fermions, which might explain also the appearance of the dark energy.

We discuss again the approach to cyclic cosmology based on the 2007 Baum–Frampton model. By introducing the relationship between entanglement entropy and space–time connectivity first introduced by Van Raamsdonck (2010) we show how vanishing entropy at the turnaround, and hence at the bounce after adiabatic contraction, can be better understood in this solution to the Tolman entropy conundrum.

A brief review of the recent astronomical data, indicating that the universe is abundantly populated by heavy black holes (BH), is presented. Conventional astrophysics and cosmology cannot explain such a high population of BHs. A mechanism of the paper of 1963 is described, which at least qualitatively explained the observational data. In particular, the prediction that massive primordial BHs can be cosmological dark matter “particles” is discussed.

The axions and axion-like particles can be detected via a resonant atomic or molecular transition induced by axion absorption. The signal obtained in this process is second order in the axion-electron interaction constant and hence small. In this chapter, it is demonstrated that this signal may become first order in the axion-electron interaction constant if we allow the interference between the axion-induced transition amplitude and the transition amplitude induced by the electromagnetic radiation. Additionally, we show that the conventional scheme of producing axions from photons in a magnetic field may be improved if the field is replaced by an atomic medium in which photons scattering off the atoms in the forward direction are transformed into axions.

We present the state-of-the-art of the numerical simulations of the supernova (SN) explosion of a carbon-oxygen core $({\mathrm{\text{CO}}}_{\mathrm{\text{core}}})$ that forms a compact binary with a neutron star (NS) companion, following the induced gravitational collapse (IGC) scenario of long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). We focus on the consequences of the hypercritical accretion of the SN ejecta onto the NS companion which either becomes a more massive NS or gravitationally collapses forming a black hole (BH). We summarize the series of results on this topic starting from the first analytic estimates in 2012 all the way up to the most recent three-dimensional (3D) smoothed-particle-hydrodynamics (SPH) numerical simulations in 2018. We present a new SN ejecta morphology, highly asymmetric, acquired by binary interaction and leading to well-defined, observable signatures in the gamma- and X-rays emission of long GRBs.

For Majorana as well as Dirac neutrinos, attempt has been made to carry out a comparative study of the predictions of Fritzsch-like texture 6, 5 and 4 zero leptonic mass matrices. In particular, considering normal hierarchy of neutrino masses, we have examined how the parameter space available to the mixing angles with respect to the lightest neutrino mass changes for the two types of neutrinos.

The implications of precision CKM measurements have been examined on the CKM paradigm as well as the CP violating parameters. Similarly, the implications of the precision neutrino oscillations measurements for the Dirac-like CP violating phase in the leptonic sector have been investigated.

I discuss the possibility of dark matter conversion into our antimatter, assuming that a part of dark matter is represented by a hypothetical mirror matter. In the Early Universe, $\mathrm{\text{B}}$ and $\mathrm{\text{L}}$ violating interactions between the particles of ordinary and mirror worlds can co-generate their baryon asymmetries in comparable amounts, ${\mathrm{\Omega }}_{\mathrm{\text{B}}}^{\prime }/{\mathrm{\Omega }}_{\mathrm{\text{B}}}=1\text{–}5$, also predicting the sign of mirror baryon asymmetry. At low energies, the same interactions induce particle mixing phenomena between two sectors. In this way, e.g. mirror neutron $n^{\prime }$ should oscillate into our antineutron $\bar{n}$, with probability that depends on environmental conditions as matter density and magnetic fields. This oscillation can be faster than the neutron decay itself, with $n^{\prime }-\bar{n}$ conversion rate accessible for the experimental search. It can have fascinating phenomenological and astrophysical consequences, and can potentially open an unlimited source of energy by transforming dark mirror matter into antimatter in a controllable way.