Grand unified theories (GUTs) may result in the E6-inspired composite Higgs model (E6CHM) at low energies, almost stabilizing the electroweak scale. We consider an orbifold GUT in 6 dimensions in which the E6-gauge group is broken to the gauge symmetry of the standard model (SM) while different multiplets of the SM fermions come from different 27-plets. The strongly coupled sector of the E6CHM is confined on the brane where E6 is broken down to its SU(6) subgroup. Near the scale of f≳5TeV, this approximate SU(6) symmetry is expected to be further broken down to its SU(5) subgroup, which contains the SM-gauge group. Such a breakdown leads to a set of pseudo-Nambu–Goldstone bosons (pNGBs) that includes an SM-like Higgs doublet. The approximate gauge coupling unification in the E6CHM takes place at high energies when the right-handed top quark is a composite fermion. To ensure anomaly cancellation, the weakly coupled sector of this model contains extra exotic matter beyond the SM. We discuss the mechanism of the generation of matter–antimatter asymmetry within the variant of the E6CHM in which the baryon number and CP invariance are violated.

The landmark discovery that neutrinos have mass and can change type (or flavour) as they propagate-a process called neutrino oscillation^1-6-has opened up a rich array of theoretical and experimental questions being actively pursued today. Neutrino oscillation remains the most powerful experimental tool for addressing many of these questions, including whether neutrinos violate charge-parity (CP) symmetry, which has possible connections to the unexplained preponderance of matter over antimatter in the Universe^7-11. Oscillation measurements also probe the mass-squared differences between the different neutrino mass states (Δm²), whether there are two light states and a heavier one (normal ordering) or vice versa (inverted ordering), and the structure of neutrino mass and flavour mixing¹². Here we carry out the first joint analysis of datasets from NOvA¹³ and T2K¹⁴, the two currently operating long-baseline neutrino oscillation experiments (hundreds of kilometres of neutrino travel distance), taking advantage of our complementary experimental designs and setting new constraints on several neutrino sector parameters. This analysis provides new precision on the Δm322 mass difference, finding 2.43-0.03+0.04×10-3eV2 in the normal ordering and -2.48-0.04+0.03×10-3eV2 in the inverted ordering, as well as a 3σ interval on δ_CP of [-1.38π, 0.30π] in the normal ordering and [-0.92π, -0.04π] in the inverted ordering. The data show no strong preference for either mass ordering, but notably, if inverted ordering were assumed true within the three-flavour mixing model, then our results would provide evidence of CP symmetry violation in the lepton sector.

We propose a distinct mechanism to explain the matter-antimatter imbalance observed in the universe, rooted in quantum entanglement asymmetry (QEA). Our concept of QEA differs from its usage in the recent literature, where it typically measures how much symmetry is broken within a subsystem of a larger quantum system. Here, we define QEA as an intrinsic asymmetry in the entanglement properties of particle-antiparticle pairs in the early universe, leading to a preferential survival of matter over antimatter. We develop a theoretical framework incorporating QEA into the standard cosmological model, providing clear justification for the asymmetry in entangled states and corresponding modifications to the Hamiltonian. Numerical simulations using lattice Quantum Chromodynamics (QCD) demonstrate that QEA can produce a net baryon asymmetry consistent with observations. We also predict specific signatures in Cosmic Microwave Background (CMB) anisotropies and large-scale structure formation, offering potential avenues for empirical verification. This work aims to deepen the understanding of cosmological asymmetries and highlight the significance of quantum entanglement in the universe's evolution.

In this thesis, we discuss ideas of how to go beyond the Standard Model (SM) of particle physics to incorporate the cosmological observations of dark matter and matter–antimatter asymmetry, and to address the theoretical problems related to the scalar sector of the SM. Although the SM has proven to be an excellent description of the interactions of elementary particles, there is both experimental and theoretical evidence that this description cannot be complete. Most notably, the cosmological observations of dark matter (DM) and the matter–antimatter asymmetry in the universe cannot be explained within the SM. We have studied simple singlet extensions of the SM. We found out that these DM and matter–antimatter-asymmetry problems cannot be solved simultaneously by adding only one real singlet scalar, but already a singlet sector consisting of the scalar and an additional fermionic DM candidate is sufficient. This study also lays the ground for more complex extensions. Further, we found out that already one additional scalar can help stabilising the SM vacuum. Another hint beyond the SM is the vast hierarchy between the mass of the Higgs boson and the Planck scale, the natural cut-off of the SM. The naturalness problem associated with light elementary scalars motivates the study of a dynamical origin behind the electroweak symmetry breaking. Whereas an underlying strongly coupled sector can explain the hierarchy between the electroweak and the Planck scales dynamically, there i

A non-GUT baryogenesis model, according to which our Universe may also contain antigalaxies is discussed. The mechanism of separation of vast quantities of matter from those of antimatter is described. The provided analysis showed that for natural range of model parameters a sufficient separation required from observational data can be obtained. Is our Universe the global baryon asymmetry or the one observed in our vicinity is just a local charactenstic? In case we assume a global character of the baryon y System consist of matter. The cosmis rays from the Sun show that our nearest star consists of matter too. In the Galactic cosmic rays the ratio of antiprotons to protons is negligible - Cosmic ray and gamma ray data exclude the possibility of noticeable amounts of antimatter in our Galaxy. The value of the baryon asymmetry observed is usually given by the ratio of the difference between the densities of baryons NB and the antibaryons NB to the photon density N-, : The data on larger scales is not so definite. We may just think that the galaxies in a cluster must be all made either of matter or of antimatter. Otherwise, we should have observed a strong annihilation radiation from the borders of the matter and antimatter regions, which is not detected. So there exist observational constraints

In this thesis, we discuss ideas of how to go beyond the Standard Model (SM) of particle physics to incorporate the cosmological observations of dark matter and matter–antimatter asymmetry, and to address the theoretical problems related to the scalar sector of the SM. Although the SM has proven to be an excellent description of the interactions of elementary particles, there is both experimental and theoretical evidence that this description cannot be complete. Most notably, the cosmological observations of dark matter (DM) and the matter–antimatter asymmetry in the universe cannot be explained within the SM. We have studied simple singlet extensions of the SM. We found out that these DM and matter–antimatter-asymmetry problems cannot be solved simultaneously by adding only one real singlet scalar, but already a singlet sector consisting of the scalar and an additional fermionic DM candidate is sufficient. This study also lays the ground for more complex extensions. Further, we found out that already one additional scalar can help stabilising the SM vacuum. Another hint beyond the SM is the vast hierarchy between the mass of the Higgs boson and the Planck scale, the natural cut-off of the SM. The naturalness problem associated with light elementary scalars motivates the study of a dynamical origin behind the electroweak symmetry breaking. Whereas an underlying strongly coupled sector can explain the hierarchy between the electroweak and the Planck scales dynamically, there i

If the Big Bang made equal amounts of matter and antimatter, then the two would annihilate and become energy. After a long time, there would be no matter and no antimatter left, just energy. But our universe today looks like it is almost all matter and hardly any antimatter. Physicists do not yet know for sure that equal amounts of matter and antimatter were created, and because of this, they are also wondering where the antimatter went, and if any was left over from the beginning of the universe. One explanation is that there was just a little bit more matter than antimatter in the beginning, so that whatever was left over after most of the matter and antimatter annihilated into energy became the mostly-matter universe we see today. Another theory is that there is lots of antimatter on the other side of the universe, hidden far beyond our vision. They could have formed their own galaxies and solar systems too. Uses Because antimatter can make so much energy, it can be used for a lot of things, such as fuel for going into outer space, or in our cars. The problem is that antimatter is very expensive to make, and is almost as expensive to store, since it cannot touch regular matter.

Neutrinos are elementary particles with many properties still unknown. Their masses so far have only upper and lower limits. Still, due to neutrino oscillations, it is clear that they are not massless, as stated by the Standard Model of Elementary Particles. Neutrinos are also present in the Universe in vast amounts, but they rarely interact with the surrounding matter. Their abundance makes them very interesting for many theories beyond the Standard Model, e.g., dark matter searches and CP symmetry violation in the leptonic sector, which could be (partially) responsible for the observed matter-antimatter asymmetry in today's Universe.\\ The Deep Underground Neutrino Experiment (DUNE) is a next-generation accelerator-based neutrino oscillation experiment that will study neutrinos with unprecedented precision and may answer many open questions. DUNE uses a powerful neutrino beam from Fermilab. It consists of a Near Detector (ND) complex to measure neutrinos before oscillat ion, and a Far Detector (FD) complex $1300\ \mathrm{km}$ away to measure them after oscillation. As part of the ND complex, measurements are also possible with different angles to the neutrino beam. This enables excellent control of systematic uncertainties of e.g., neutrino cross section measurements.\\ One detector in the near detector complex is The Muon Spectrometer (TMS), an extension of a Liquid Argon (LAr) detector that measures the charge and momentum of muons produced in neutrino interactions within

of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are The multiverse is the hypothetical set of all universes. Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are called "parallel universes", "flat universes", "other universes", "alternate universes", "multiple unive There are models of two related universes that e.g. attempt to explain the baryon asymmetry – why there was more matter than antimatter at the beginning – with a mirror anti-universe. One two-universe cosmological model could explain the Hubble constant (H0) tension via interactions between the two worlds. The "mirror world" would contain copies of all existing fundamental particles. Another twin/pair-world or "bi-world" cosmology is shown to theoretically be able to solve the cosmological constant (Λ) problem, closely related to dark energy: two interacting worlds with a large Λ each could result in a small shared effective Λ.