Standard Sector Research Articles

Analysis of Metaverses Structure and Characteristics

Statement of the problem: The fundamental changes currently taking place in the development of networks and communication systems are concentrated in the concept of creating metaverses. Despite the fact that this concept appeared within the framework of the International Telecommunication Union only in 2023, research in this area already occupies the first line in scientific publications on networks and communication systems. In the Russian Federation, this area of investigation is currently not given the required attention. The goal of the paper is to analyze the documents of the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T) and determine the structure and characteristics of metaverses based on the results of the ITU-T focus group on metaverses. The method used is systems analysis. Result: definition, structure, including virtual and mirror worlds, characteristics of metaverses. Novelty: The conducted analysis allowed us to define the concept of the metaverse and its constituent worlds: virtual world and mirror world, as well as an important feature of metaverses such as logging, which is a log of the life of users and objects. These results allow us to accurately determine the vector of further research. Theoretical/Practical significance: a fundamental definition of metaverses, their structure and characteristics are obtained. From a practical point of view, the results obtained make it possible to begin a set of scientific investigations on metaverses on conceptual and systemic basis that meets international standards.

Relic density and temperature evolution of a light dark sector

We have developed a set of four fully coupled Boltzmann equations to precisely determine the relic density and temperature of dark matter by including three distinct sectors: dark matter, light scalar, and standard model sectors. The intricacies of heat transfer between dark matter (DM) and the standard model sector through a light scalar particle are explored, inspired by stringent experimental constraints on the scalar-Higgs mixing angle and the DM-scalar coupling. Three distinct sectors emerge prior to DM freeze-out, requiring fully coupled Boltzmann equations to accurately compute relic density. Investigation of forbidden, resonance, and secluded DM scenarios demonstrates significant deviations between established methods and the novel approach with fully coupled Boltzmann equations. Despite increased computational demands, this emphasizes the need for improved precision in relic density calculations, underlining the importance of incorporating these equations in comprehensive analyses. Published by the American Physical Society 2024

Dissecting polytopes: Landau singularities and asymptotic expansions in 2 → 2 scattering

Parametric representations of Feynman integrals have a key property: many, frequently all, of the Landau singularities appear as endpoint divergences. This leads to a geometric interpretation of the singularities as faces of Newton polytopes, which facilitates algorithmic evaluation by sector decomposition and asymptotic expansion by the method of regions. Here we identify cases where some singularities appear instead as pinches in parametric space for general kinematics, and we then extend the applicability of sector decomposition and the method of regions algorithms to such integrals, by dissecting the Newton polytope on the singular locus. We focus on 2 → 2 massless scattering, where we show that pinches in parameter space occur starting from three loops in particular nonplanar graphs due to cancellation between terms of opposite sign in the second Symanzik polynomial. While the affected integrals cannot be evaluated by standard sector decomposition, we show how they can be computed by first linearising the graph polynomial and then splitting the integration domain at the singularity, so as to turn it into an endpoint divergence. Furthermore, we demonstrate that obtaining the correct asymptotic expansion of such integrals by the method of regions requires the introduction of new regions, which can be systematically identified as facets of the dissected polytope. In certain instances, these hidden regions exclusively govern the leading power behaviour of the integral. In momentum space, we find that in the on-shell expansion for wide-angle scattering the new regions are characterised by having two or more connected hard subgraphs, while in the Regge limit they are characterised by Glauber modes.

Search for strongly interacting dark matter at Belle II

A small component of dark matter (DM) that is strongly interacting with the standard model sector is consistent with various experimental observations. Despite the small abundance, strongly interacting DM can lead to pronounced signals in DM direct detection experiments. We study Belle II sensitivity on strongly interacting DM that has a MeV-GeV mass and couples with electrons. By taking into account the substantial interactions between DM and electrons within detectors, we compute the “ceiling” of the monophoton signature at Belle II, beyond which the monophoton channel loses its sensitivity, and visible electromagnetic calorimeter (ECL) clusters due to DM scatterings assume significance. We study two ECL signatures for strongly interacting DM: the monocluster and the dicluster channels. To carry out detailed calculations and to compare with other constraints, we consider DM models with light mediators, as they naturally lead to sizable interaction cross sections. We compute exclusion regions for the dicluster, monocluster, and monophoton channels. We find that Belle II (with currently accumulated data of 362 fb−1) can rule out a significant portion of the parameter space above the ceilings of the constraints from various DM direct detection and neutrino experiments, for the vector mediator case with mass ≳10 MeV. Belle II also offers superior constraints on new light particles compared to primordial black hole (PBH) for the scalar mediator with mass ≳10 MeV. Published by the American Physical Society 2024

Collider signatures of near-continuum dark matter

In this paper we study a near-continuum dark matter model, in which dark sector consists of a tower of closely spaced states with weak-scale masses. We construct a five-dimensional model which naturally realizes this spectrum. The dark matter is described by a bulk field, which interacts with the brane-localized Standard Model sector via a Z portal. We then study collider signatures of this model. Near-continuum dark matter states produced in a collider undergo cascade decays, resulting in events with high multiplicity of jets and leptons, large missing energy, and displaced vertices. A custom-built Monte Carlo tool described in this paper allows for detailed simulation of the signal events. We present results of such simulations for the case of electron-positron collisions.

Detecting Environmental Conditions in Cultivation Lands Using Bionic Devices

Climate change has an impact on crops, fruits, vegetables, and pest infestation, hence agricultural output is a top priority for most nations. As a result, professional growers have the problem of reaching maximum output results, and greenhouses have emerged as an excellent choice for ensuring these results. Farmers can employ innovative technologies inside greenhouses to prevent insect damage to plants and increase indoor growth through climate management. However, in order to manage agricultural fields and greenhouses successfully, farmers must now use Industry 4.0 technology such as robotics, Internet of Things devices, machine learning software, and so on. In this setting, sensor deployment is critical for gathering data and obtaining knowledge to help farmers make decisions. As a practical option for small farms, this research proposes an autonomous robot that drives along greenhouse crop paths with previously specified routes and can collect environmental data provided by a wireless sensor network when the farmer has no prior knowledge of the crop. An unsupervised learning method is used to cluster the optimal, standard, and deficient sectors of a greenhouse in order to identify improper crop development patterns. Finally, a user interface is built to assist farmers in planning the robot's route and distance while gathering sensor data to monitor crop conditions.

Dissipative Dark Substructure: The Consequences of Atomic Dark Matter on Milky Way Analog Subhalos

Abstract Using cosmological hydrodynamical zoom-in simulations, we explore the properties of subhalos in Milky Way analogs that contain a subcomponent of atomic dark matter (ADM). ADM differs from cold dark matter (CDM) due to the presence of self-interactions that lead to energy dissipation, analogous to standard model baryons. This model can arise in dark sectors that are natural and theoretically motivated extensions to the standard model. The simulations used in this work were carried out using GIZMO and utilize the FIRE-2 galaxy formation physics in the standard model baryonic sector. For the parameter points we consider, the ADM gas cools efficiently, allowing it to collapse to the center of subhalos. This increases a subhalo’s central density and affects its orbit, with more subhalos surviving small pericentric passages. The subset of subhalos that host satellite galaxies have cuspier density profiles and smaller stellar half-mass radii relative to CDM. The entire population of dwarf galaxies produced in the ADM simulations is more compact than those seen in CDM simulations, unable to reproduce the entire diversity of observed dwarf galaxy structures. Additionally, we also identify a population of highly compact subhalos that consist nearly entirely of ADM and form in the central region of the host, where they can leave distinctive imprints in the baryonic disk. This work presents the first detailed exploration of subhalo properties in a strongly dissipative dark matter scenario, providing intuition for how other regions of ADM parameter space, as well as other dark sector models, would impact galactic-scale observables.

Predictions for neutrinos and new physics from forward heavy hadron production at the LHC

Scenarios with new physics particles feebly interacting with the Standard Model sector provide compelling candidates for dark matter searches. Geared with a set of new experiments for the detection of neutrinos and long-lived particles the Large Hadron Collider (LHC) has joined the hunt for these elusive states. On the theoretical side, this emerging physics program requires reliable estimates of the associated particle fluxes, in particular those arising from heavy hadron decays. In this work, we provide state-of-the-art QCD predictions for heavy hadron production including radiative corrections at next-to-leading order and using parton distribution functions including small-x resummation at next-to-leading logarithmic accuracy. We match our predictions to parton showers to provide a realistic description of hadronisation effects. We demonstrate the utility of our predictions by presenting the energy spectrum of neutrinos from charm hadron decays. Furthermore, we employ our predictions to estimate, for the first time, FASER’s sensitivity to electrophilic ALPs, which are predominantly generated in beauty hadron decays.

Twin sterile neutrino dark matter

We propose that the dark matter of our Universe could be sterile neutrinos which reside within the twin sector of a mirror twin Higgs model. In our scenario, these particles are produced through a version of the Dodelson-Widrow mechanism that takes place entirely within the twin sector, yielding a dark matter candidate that is consistent with x-ray and gamma-ray line constraints. Furthermore, this scenario can naturally avoid the cosmological problems that are typically encountered in mirror twin Higgs models. In particular, if the sterile neutrinos in the Standard Model sector decay out of equilibrium, they can heat the Standard Model bath and reduce the contributions of the twin particles to Neff. Such decays also reduce the effective temperature of the dark matter, thereby relaxing constraints from large-scale structure. The sterile neutrinos included in this model are compatible with the seesaw mechanism for generating Standard Model neutrino masses. Published by the American Physical Society 2024

Lepton universality in a model with three generations of sterile Majorana neutrinos

The extension of the Standard Model lepton sector by three right-handed Majorana neutrinos [heavy neutral leptons (HNLs)] with masses up to GeV scale is considered. While the lightest heavy neutral lepton is the dark matter particle with mass of the order of 5 keV, the remaining two HNLs ensure standard (active) neutrino mass generation by means of the seesaw type I mechanism. Two heavy sterile neutrinos with quasidegenerate masses up to 5 GeV can induce the deviation of lepton universality violation parameter in the decays of π+ and K+ mesons from the Standard Model value. Contours are obtained for the permissible values of this parameter within the framework of two mixing scenarios, taking into account the lifetime boundary for heavy neutral lepton from big bang nucleosynthesis in the Universe. When calculating the HNL decay width in the framework of the model with six Majorana neutrinos, three active and three heavy, both two-particle and three-particle lepton decays, essential for masses below the mass of the pion, were taken into account. When calculating the decay widths, the limiting case known as the “Dirac limit” is not used. The results based on the explicit form of mixing matrices for three HNL generations and the diagram technique for Majorana neutrinos, which explicitly take into account the interference terms for diagrams with identical mass states, can lead to some differences in lifetime from the results using the Dirac limit and the displacement of the corresponding experimental exclusion contours of the “mass-mixing” type. For the second mixing scenario, a mass region of 460 MeV<M<485 MeV has been found that allows violation of lepton universality in charged kaon decays at the level observed in the experiment. Published by the American Physical Society 2024

Non-gravitational signals of dark energy under a gauge symmetry

We investigate non-gravitational signals of dark energy within the framework of gauge symmetry in the dark energy sector. Traditionally, dark energy has been primarily studied through gravitational effects within general relativity or its extensions. On the other hand, the gauge principles have played a central role in the standard model sector and dark matter sector. If the dark energy field operates under a gauge symmetry, it introduces the possibility of studying all major components of the present universe under the same gauge principle. This approach marks a significant shift from conventional methodologies, offering a new avenue to explore dark energy.

The relevance of the country and sector effect in global equity returns around COVID-19 and developed and emerging markets

This study explores the historical and current explanatory power of country classification and Global Industry Classification Standard sector classification on global equity returns in the equally weighted MSCI All Country World Index. R2 is a crucial statistical tool for risk and portfolio management professionals because it serves as a measure of how much of a portfolio's movements can be explained by factors. Its significance lies in its ability to quantify how dependent a portfolio's risk is on those factors. The country classification's adjusted R2 is dominant in global equities, driven by its dominance within emerging markets (EM). Within developed markets (DM), the country effect's slight dominance over the sector effect has decreased over time — the two have become more balanced since 2015, with the sector effect having a slightly higher adjusted R2 value. There was a drop in the R2 for all classifications during the COVID-19 pandemic. This drop was most significant in the country classification, with a sharp decline to 8.3 per cent, well below its previous historical minimum of 12 per cent, before it rebounded to its historical range. This change drove further analysis into the country effect across EM and DM, where the large drop and rebound were primarily within EM. During this time, the sector effect dropped but remained within its historical range, implying a larger loss of diversification benefit in country effect than in sector effect. The impact of Chinese stocks on country effect within EM is also investigated. In 2018, there was a large influx of Chinese companies into the index, which caused a decline in country diversification and hence a reduction in explanatory power within EM. China's rapid and strict COVID-19 response, early tight monetary policy and regulatory crackdown have since caused it to become increasingly differentiated from the rest of EM, increasing country diversification within EM and causing the accentuated rebound in explanatory power of the country effect post-COVID-19. Risk managers can use these results to validate the use of sector and country classifications in portfolio construction.

Primordial black hole versus inflaton

We compare the dark matter (DM) production processes and its parameters space in the background of reheating obtained from two chief systems in the early Universe: the inflaton ϕ and the primordial black holes (PBHs). We concentrated on the mechanism where DMs are universally produced only from the PBH decay and the generation of the standard model plasma from both inflaton and PBHs. Whereas the distribution of primordial black holes behaves like dust, the inflaton phenomenology depends strongly on its equation of state after the inflationary phase, which in turn is conditioned by the nature of the potential V(ϕ). Depending upon the initial mass and population of PBHs, a large range of DM mass is shown to be viable if reheating is controlled by PBHs itself. Inflaton-dominated reheating is observed to further widen such possibilities depending on the initial population of black holes and its mass as well as the coupling of the inflaton to the standard model sector. Published by the American Physical Society 2024

The basis invariant flavor puzzle

The flavor puzzle of the Standard Model quark sector is formulated in a non-perturbative way, using basis invariants that are independent of the choice of quark field basis. To achieve this, we first derive the algebraic ring of 10 CP even (primary) and 1 CP odd (secondary) basis invariants, using the Hilbert series and plethystic logarithm. An orthogonal basis in the ring of basis invariants is explicitly constructed, using hermitian projection operators derived via birdtrack diagrams. The thereby constructed invariants have well defined CP transformation behavior and give the most direct access to the flavor symmetric alignments of basis covariants. We firstly “measure” the orthogonal basis invariants from experimental data and characterize their location in the available parameter space. The experimentally observed orthogonal basis invariants take very close to maximal values and are highly correlated. Explaining the location of the invariants at close to maximal points, including the associated miniscule and highly correlated deviations, corresponds to solving the flavor puzzle in the invariant language. Once properly normalized, the orthogonal basis invariants are close to scale (RGE) invariant, hence, provide exquisite targets for fits of both, low- and high-scale (bottom-up and top-down) flavor models. Our result provides an entirely new angle on the flavor puzzle, and opens up ample opportunities for its ultimate exploration.

Implications of an enhanced B→Kνν¯ branching ratio

Rare decays mediated by b→sνν¯ transitions have been reported by the Belle II experiment. The branching ratio of the decay B+→K+νν¯ is found to be enhanced with respect to the standard model value. If taken at face value, the implications are profound; either lepton flavor universality is violated at the (multi)-TeV-scale, or light new physics is involved. This holds in general if B(B+→K+νν¯) exceeds 1.2×10−5(1.3×10−5) at 1σ (2σ), which tightens with a decreasing upper limit on B(B→K*νν¯), that is in reach of the Belle II experiment. In view of the strong constraints on electron-muon universality violation in |Δb|=|Δs|=1 processes, viable explanations are heavy, (5–10)-TeV tree-level new physics mediators that couple only to tau-flavors, or lepton flavor violating ones. In addition, couplings of similar size to both left- and right-handed quarks are generically required, implying nonminimal beyond the standard model sectors which are carefully balanced against flavor constraints. The decay Bs0→invisibles can shed light on whether new physics is light or heavy. In the former case, branching ratios can be as large as 10−5. Published by the American Physical Society 2024

The need for stronger international support to integrate health and well-being and transform education: a perspective on developing countries.

The reciprocal relationship between education and health is well-established, emphasizing the need for integrating health, nutrition, and well-being components into educational sector planning. Despite widespread acknowledgment of this need, countries lack concrete measures to achieve this integration. We examine challenges that countries have faced and the progress they have made in integrating these components into education sector plans and review the extent to which existing educational planning guidelines and tools address health and well-being. The review reveals a significant underrepresentation of health, well-being, and related themes in existing educational planning frameworks. Recent tools and frameworks developed to support a more holistic approach to education have not yet been widely adopted in standard education sector planning processes. The implementation of such approaches remains inconsistent, with significant barriers including limited cross-sectoral collaboration, lack of capacity, and insufficient funding, among others. Addressing these gaps requires improved guidance, technical support, and a multisectoral approach to education planning that includes health, nutrition, and well-being as fundamental components of foundational learning, supported by political commitment, capacity, and adequate financing.

Possible Search for Majorana Neutrinos at Future Lepton Colliders

We discuss the processℓ+ℓ−→NW±ℓ∓, whereNis a heavy Majorana neutrino andℓ=e,μ. Large cross sections are expected for these processes at high center-of-mass energies, which can be reached at future lepton–lepton colliders. The Monte Carlo simulation of the studied processes is produced within the framework of the seesaw type-I model, where the Majorana neutrinos (or heavy neutral leptons, HNL), are introduced in the standard leptonic sector. Recently the possibility to search for the direct HNL production was studied in theℓ+ℓ−→Nνℓprocess with the subsequent decayN→W±ℓ∓. In this paper we investigate an alternative processℓ+ℓ−→NW±ℓ∓→W±W±ℓ∓ℓ∓with the lepton number violation by two units. The similar processes appear in collisions with the same-sign beams,e−e−→NW−e−→W−W−e+e−orμ+μ+→NW+μ+→W+W+μ+μ−. The cross sections of the processes under consideration are enhanced by the soft photon exchange in thet-channel. We calculate the cross sections for the signals and potential Standard Model backgrounds for thee+e−beam collisions at the 1 TeV center-of-mass energy and theμ+μ−collisions at 3 and 10 TeV. Due to the diagrams with softt-channel photons and respective interference the promptly emitted leptons are produced in the direction close to the corresponding beam. These leptons will be lost in the beam pipe or badly measured by forward detectors. However, the signal events can be well separated from backgrounds using the rest of the event containing theWWℓparticles. Finally, the expected upper limits on the mixing parameters|VℓN|2as a function ofM(N) are calculated.

Dark dimension gravitons as dark matter

We consider cosmological aspects of the Dark Dimension (a mesoscopic dimension of micron scale), which has recently been proposed as the unique corner of the quantum gravity landscape consistent with both the Swampland criteria and observations. In particular we show how this leads, by the universal coupling of the Standard Model sector to bulk gravitons, to massive spin 2 KK excitations of the graviton in the dark dimension (the “dark gravitons”) as an unavoidable dark matter candidate. Assuming a lifetime for the current de Sitter phase of our universe of order Hubble, which follows from both the dS Swampland Conjecture and TCC, we show that generic features of the dark dimension cosmology can naturally lead to the correct dark matter density and a resolution of the cosmological coincidence problem, where the matter/radiation equality temperature (T ~ 1 eV) coincides with the temperature where the dark energy begins to dominate. Thus one does not need to appeal to Weinberg’s anthropic argument to explain this coincidence. The dark gravitons are produced at T ~ 4 GeV, and their composition changes as they mainly decay to lighter gravitons, without losing much total mass density. The mass of dark gravitons is mDM ∼ 1 − 100 keV today.

Modelling and numerical analysis of combined dual impact of SRS and FWM on the performance of upstream and downstream channels of a novel UDWDM/DWDM-PON

Wavelength division multiplexing (WDM) is an important method in modern optical communication systems for both long-haul and access networks. Particularly, after being standardized by Telecommunication Standardization Sector of International Telecommunication Union (ITU-T), WDM passive optical network (WDM-PON) becomes a considerable choice for fronthaul implementations of 5G networks. Stimulated Raman scattering (SRS) and four-wave mixing (FWM) are crucial nonlinear impacts that significantly limit the performance of WDM-based optical fiber communication systems. In this paper, an ultra-dense/dense WDM-PON (UDWDM/DWDM-PON) architecture has been proposed and combined dual impact of SRS and FWM on performances of upstream channels (USCs) and downstream channels (DSCs) of the proposed UDWDM/DWDM-PON has been numerically analyzed. USCs have been assumed to operate in 1310 nm region while operating wavelength region of DSCs has been taken as 1550 nm. Simulations have been performed on both UDWDM-PON architectures with 3.125 GHz and 6.25 GHz channel spacings and DWDM-PON architectures with channel spacings between 12.5 GHz and 100 GHz. 2x15-channel and 2x63-channel system structures have been considered in simulations. Signal-to-crosstalk ratio (SXR) has been chosen as performance parameter and its variation with channel input powers, channel spacings and channel lengths have been simulated for both USCs and DSCs of 2x15- and 2x63-channel UDWDM/DWDM-PONs. Results show that the proposed UDWDM/DWDM-PONs using single G.652 fiber can exhibit a reliable communication with minimum 23 dB SXR performance under combined dual impact of SRS and FWM unless some highlights about input powers and channel lengths mentioned in the paper are neglected.

Possible Search for Majorana Neutrinos at Future Lepton Colliders

We discuss the process {{ell }^{ + }}{{ell }^{ - }} to N{{W}^{ pm }}{{ell }^{ mp }}, where N is a heavy Majorana neutrino and ell = e,mu . Large cross sections are expected for these processes at high center-of-mass energies, which can be reached at future lepton–lepton colliders. The Monte Carlo simulation of the studied processes is produced within the framework of the seesaw type-I model, where the Majorana neutrinos (or heavy neutral leptons, HNL), are introduced in the standard leptonic sector. Recently the possibility to search for the direct HNL production was studied in the {{ell }^{ + }}{{ell }^{ - }} to N{{nu }_{ell }} process with the subsequent decay N to {{W}^{ pm }}{{ell }^{ mp }}. In this paper we investigate an alternative process {{ell }^{ + }}{{ell }^{ - }} to N{{W}^{ pm }}{{ell }^{ mp }} to {{W}^{ pm }}{{W}^{ pm }}{kern 1pt} {{ell }^{ mp }}{kern 1pt} {{ell }^{ mp }} with the lepton number violation by two units. The similar processes appear in collisions with the same-sign beams, {{e}^{ - }}{{e}^{ - }} to N{{W}^{ - }}{kern 1pt} {{e}^{ - }} to {{W}^{ - }}{kern 1pt} {{W}^{ - }}{kern 1pt} {{e}^{ + }}{kern 1pt} {{e}^{ - }} or {{mu }^{ + }}{{mu }^{ + }} to N{{W}^{ + }}{kern 1pt} {{mu }^{ + }} to {{W}^{ + }}{kern 1pt} {{W}^{ + }}{kern 1pt} {{mu }^{ + }}{kern 1pt} {{mu }^{ - }}. The cross sections of the processes under consideration are enhanced by the soft photon exchange in the t-channel. We calculate the cross sections for the signals and potential Standard Model backgrounds for the {{e}^{ + }}{{e}^{ - }} beam collisions at the 1 TeV center-of-mass energy and the {{mu }^{ + }}{{mu }^{ - }} collisions at 3 and 10 TeV. Due to the diagrams with soft t-channel photons and respective interference the promptly emitted leptons are produced in the direction close to the corresponding beam. These leptons will be lost in the beam pipe or badly measured by forward detectors. However, the signal events can be well separated from backgrounds using the rest of the event containing the WWell particles. Finally, the expected upper limits on the mixing parameters {{left| {{{V}_{{ell N}}}} right|}^{2}} as a function of M(N) are calculated.