Large Extra Dimensions Research Articles

Signatures of bulk neutrinos in the early Universe

Neutrino masses and quantum gravity are strong reasons to extend the standard model of particle physics. A large extra dimension can be motivated by quantum gravity and can explain the small neutrino masses with new singlet states that propagate in the bulk. In such a case, a Kaluza-Klein tower of sterile neutrinos emerges. We revisit constraints on towers of sterile neutrinos that come from cosmological observables such as the effective number of noninteracting relativistic species and the dark matter density. These limits generically rule out micron-sized extra dimensions. We explore the weakening of these constraints to accommodate an extra dimension close to the micron size by assuming that the Universe is reheated after inflation to a low temperature. We discuss how such a possibility can be distinguished in the event of a positive signal in a cosmological observable. Published by the American Physical Society 2024

Search for new physics in high-mass diphoton events from proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{\ extrm{s}} $$\\end{document} = 13 TeV

Results are presented from a search for new physics in high-mass diphoton events from proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV. The data set was collected in 2016–2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb−1. Events with a diphoton invariant mass greater than 500 GeV are considered. Two different techniques are used to predict the standard model backgrounds: parametric fits to the smoothly-falling background and a first-principles calculation of the standard model diphoton spectrum at next-to-next-to-leading order in perturbative quantum chromodynamics calculations. The first technique is sensitive to resonant excesses while the second technique can identify broad differences in the invariant mass shape. The data are used to constrain the production of heavy Higgs bosons, Randall-Sundrum gravitons, the large extra dimensions model of Arkani-Hamed, Dimopoulos, and Dvali (ADD), and the continuum clockwork mechanism. No statistically significant excess is observed. The present results are the strongest limits to date on ADD extra dimensions and RS gravitons with a coupling parameter greater than 0.1.

Nonlinear wave propagation in large extra spatial dimensions and the blackbody thermal laws

Abstract Nonlinear wave propagation in large extra spatial dimensions (on and above d = 2) is investigated in the context of nonlinear electrodynamics theories that depend exclusively on the invariant F ( = − ( 1 / 4 ) F μ ν F μ ν ) . In this vein, we consider propagating waves under the influence of external uniform electric and magnetic fields. Features related to the blackbody radiation in the presence of a background constant electric field such as the generalization of the spectral energy density distribution and the Stefan–Boltzmann law are obtained. Interestingly enough, anisotropic contributions to the frequency spectrum appear in connection to the nonlinearity of the electromagnetic field. In addition, the long wavelength regime and Wien’s displacement law in this situation are studied. The corresponding thermodynamics quantities at thermal equilibrium, such as energy, pressure, entropy, and heat capacity densities are contemplated as well.

Gravitational waves from primordial black hole evaporation with large extra dimensions

The spectra of gravitational waves from black hole evaporation generically peak at frequencies of order the Hawking temperature, making this signal ultra-high frequency for primordial black holes evaporating in the early universe. This motivates us to consider small black holes in theories with large extra dimensions, for which the peak frequency can be lowered substantially, since the true bulk Planck scale M * can be much smaller than the effective M Pl. We study the emission of brane-localized gravitons during the Hawking evaporation of ultra-light primordial black holes in the context of theories with large extra dimensions, with the ultimate goal of computing the contribution to the stochastic gravitational wave background. To accurately model black hole evolution, we compute greybody factors for particles of spin-0, 1/2, 1, and 2 emitted on the brane and in the bulk, presuming the majority of emission proceeds during the Schwarzschild phase. We then compute the power spectrum and present day spectral density parameter for brane-localized gravitons contributing to a gravitational wave signal. We find that for an optimal choice of parameters, the peak frequency plateaus in the sub-MHz regime, within range of planned high-frequency gravitational wave detectors, making this scenario a target for detection once their sensitivity exceeds ΔN eff bounds.

Large extra dimensions from higher-dimensional inflation

We propose the possibility that compact extra dimensions can obtain large size by higher-dimensional inflation, relating the weakness of the actual gravitational force to the size of the observable Universe. Solution to the horizon problem implies that the fundamental scale of gravity is smaller than 1013 GeV, which can be realized in a braneworld framework for any number of extra dimensions. However, requirement of an (approximate) flat power spectrum of primordial density fluctuations consistent with present observations makes this simple proposal possible only for one extra dimension at around the micron scale. After the end of five-dimensional inflation, the radion modulus can be stabilized at a vacuum with positive energy of the order of the present dark energy scale. An attractive possibility is based on the contribution to the Casimir energy of right-handed neutrinos with a mass at a similar scale. Published by the American Physical Society 2024

Machine learning classification of sphalerons and black holes at the LHC

In models with large extra dimensions, “miniature” black holes (BHs) might be produced in high-energy proton–proton collisions at the Large Hadron Collider (LHC). In the semi-classical regime, those BHs thermally decay, giving rise to large-multiplicity final states with jets and leptons. On the other hand, similar final states are also expected in the production of electroweak sphaleron/instanton-induced processes. We investigate whether one can discriminate these scenarios when BH or sphaleron-like events are observed in the LHC using machine learning (ML) methods. Classification among several BH scenarios with different numbers of extra dimensions and the minimal BH masses is also examined. In this study we consider three ML models: XGBoost algorithms with (1) high- and (2) low-level inputs, and (3) a Residual Convolutional Neural Network. In the latter case, the low-level detector information is converted into an input format of three-layer binned event images, where the value of each bin corresponds to the energy deposited in various detector subsystems. We demonstrate that only a small number of detected events are sufficient to effectively discriminate between the sphaleron and BH processes. Separation between BH scenarios with different minimal masses is possible with an order of 10 events passing the preselection. A sufficient number of events could be observed in combined Run-2 and -3 data, if the production cross section is not much smaller than the present limit ∼0.1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim 0.1$$\\end{document} fb. We find, however, that a large number of events is needed to discriminate between BH hypotheses with the same minimal BH mass, but different numbers of extra dimensions.

Kaluza-Klein spectroscopy from neutron oscillations into hidden dimensions

Neutrons and neutrinos are natural probes for new physics. Since they carry no conserved gauge quantum numbers, both can easily mix with the fermions from hidden sectors. A particularly interesting effect is the oscillation of a neutron or a neutrino into a fermion propagating in large extra dimensions. In fact, such a mixing has been identified as the possible origin of small neutrino mass. In this paper, we study neutron oscillations into an extradimensional fermion and show that this effect provides a resonance imaging of the Kaluza-Klein tower. The remarkable feature of this phenomenon is its generic nature: because of a fine spacing of the Kaluza-Klein tower, neutrons at a variety of energy levels, both free or within nuclei, find a bulk oscillation partner. In particular, the partner can be a Kaluza-Klein mode of the same species that gives mass to the neutrino. The existence of bulk states matching the neutron energy levels of nuclear spectra gives rise to tight constraints as well as to potentially observable effects. For a free neutron, we predict recurrent resonant oscillations occurring with the values of the magnetic field correlated with the KK levels. We derive bounds on extra dimensions from ultracold neutron experiments and suggest signatures for refined measurements, which, in particular, can probe the parameter space motivated by the hierarchy problem. Ultracold neutron experiments offer a unique way of Kaluza-Klein spectroscopy. Published by the American Physical Society 2024

DEVELOPMENT OF A VIRTUAL-BASED SKILL COMPETENCY TEST (UKK) PRACTICUM MODEL IN VOCATIONAL SCHOOLS DEPARTMENT OF COMPUTER NETWORKING ENGINEERING

Abstract This study aims to determine: (1) the stages of developing a virtual-based UKK practicum model in the Network Computer Engineering Laboratory at SMK Negeri Labuang. (2) Development of a virtual-based UKK practicum model majoring in computer network engineering is valid, practical and effective as a result of development. The research method used is the method of research and development or Research and Development. The process of developing a virtual-based UKK practicum model refers to the ADDED development model which is a new development model resulting from descriptive analysis, critical analysis, and comparative analysis. The ADDED model stages include: (1) the Analyze stage, namely the analysis of the need for a computer / laptop as hardware, the availability of internet services, a computer laboratory while the application needs as software. (2) The Design Stage, namely the sequence or steps of making a design for the development of a practicum model, namely the required applications. (3) Development stage, namely product development in the form of a practicum model with a simulation model design specification. (4) Evaluate and Revise stage, namely steps in assessing and testing the validity, practicality, and effectiveness; (5) Dissemination and Implementation Stage, namely the process of disseminating and implementing the practicum model development. Assessment and testing is carried out by competent experts or experts, namely media and network computer techniques, while the testing is carried out through limited individual and group trials. The results of the assessment show that the development of a virtual-based UKK practicum model has fulfilled its validity by covering aspects of display, virtual and programming, the test results show that it is practical and effective. The development of the virtual-based UKK practicum model is said to be practical because it is in the very good category, it is said to be effective because the results of the evaluation carried out have met or reached the predetermined passing standard value. The development of a virtual-based UKK practicum model that was developed met the criteria of being valid, practical, and effective. For this reason, it is suggested that the virtual-based UKK practicum model can be used as a media for learning simulation for students majoring in network computer engineering in dealing with UKK SMK as well as a reference for tutors to conduct a practice orientation period, practice using practical tools. Keywords: Development, Model, Virtual UKK Practicum

Perils of towers in the swamp: dark dimensions and the robustness of EFTs

Recently there has been an interesting revival of the idea to use large extra dimensions to address the dark energy problem, exploiting the (true) observation that towers of states with masses split, by MN2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {M}_N^2 $$\\end{document} = f(N)m2, with f an unbounded function of the integer N, sometimes contribute to the vacuum energy only an amount of order mD in D dimensions. It has been argued that this fact is a consequence of swampland conjectures and may require a departure from Effective Field Theory (EFT) reasoning. We test this claim with calculations for Casimir energies in extra dimensions. We show why the domain of validity for EFTs ensures that the tower spacing scale m is always an upper bound on the UV scale for the lower-energy effective theory; use of an EFT with a cutoff part way up a tower is not a controlled approximation. We highlight the role played by the sometimes-suppressed contributions from towers in extra-dimensional approaches to the cosmological constant problem, old and new, and point out difficulties encountered in exploiting it. We compare recent swampland realizations of these arguments with earlier approaches using standard EFT examples, discussing successes and limitations of both.

Capability of the proposed long-baseline experiments to probe large extra dimension

Capability of the proposed long-baseline experiments to probe large extra dimension

Corrigendum: Dimensionally-dependent uncertainty relations, or why we (probably) won’t see micro-black holes at the LHC, even if large extra dimensions exist

Corrigendum: Dimensionally-dependent uncertainty relations, or why we (probably) won’t see micro-black holes at the LHC, even if large extra dimensions exist

ПРЕЦЕССИЯ ЛЕНЗЕ-ТИРРИНГА ЧЕРНЫМИ ДЫРАМИ В МОДЕЛИ РЭНДАЛЛА-САНДРАМА

The description of our universe on a brane suggests a large extra dimension and a fundamental scale of gravity, which can be several orders of magnitude lower than the Planck scale. An interesting consequence of the brane world scenario is the nature of spherically symmetric vacuum solutions of the brane gravitational field equations, which can represent black holes with properties quite different from those of ordinary black holes in 4 dimensions. The paper investigates the Lense-Thirring precession by black holes in the Randall-Sandrum model caused by the frame-dragging effect. Lense-Thirring precession is a general relativistic effect that occurs when a rotating particle is displaced vertically from the equatorial axis of a rotating body in such a way that the framedragging causes oscillations around the ecliptic and periapsis. The Randall-Sandrum model assumes that our universe is a negative tension domain wall separated from the positive tension wall by an anti-de Sitter space slab. The space-time of a black hole in the Randall-Sandrum model of the "brane world" theory is characterized by an induced tidal charge. In particular, a generalized expression for the Lense-Thirring precession rate in the case of a strong and weak gravitational field is obtained. Further, the precession of the gyroscope in the plane θ=0 is considered, the dependence of the Lense-Thirring precession rate for a stellar-mass black hole and a supermassive black hole is shown for different values of the tidal charge β. The results of numerical simulation are presented for various values of the tidal charge and the radial coordinate.

Dimensionally-dependent uncertainty relations, or why we (probably) won’t see micro-black holes at the LHC, even if large extra dimensions exist

We present a simple gedanken experiment in which a compact object traverses a spacetime with three macroscopic spatial dimensions andncompact dimensions. The compactification radius is allowed to vary, as a function of the object’s position in the four-dimensional space, and we show that the conservation of gravitational self-energy implies the dimensional dependence of the mass-radius relation. In spacetimes with extra dimensions that are compactified at the Planck scale, no deviation from the four-dimensional result is found, but, in spacetimes with extra dimensions that are much larger than the Planck length, energy conservation implies a deviation from the normal Compton wavelength formula. The new relation restores the symmetry between the Compton wavelength and Schwarzschild radius lines on the mass-radius diagram and precludes the formation of black holes at TeV scales, even if large extra dimensions exist. We show how this follows, intuitively, as a direct consequence of the increased gravitational field strength at distances below the compactification scale. Combining these results with the heuristic identification between the Compton wavelength and the minimum value of the position uncertainty, due to the Heisenberg uncertainty principle, suggests the existence of generalised, higher-dimensional uncertainty relations. These relations may be expected to hold for self-gravitating quantum wave packets, in higher-dimensional spacetimes, with interesting implications for particle physics and cosmology in extra-dimensional scenarios.

Stringy realization of a small and positive cosmological constant in dark bubble cosmology

In this paper we construct a stringy embedding of the dark bubble model of an expanding 4D cosmology with the help of branes rotating in extra dimensions. The Universe rides a bubble which has nucleated in an unstable higher dimensional background. Our construction is therefore a string theoretical realization of Vilenkin's quantum cosmology. While the cosmological constant vanishes at lowest order, loop corrections predicted by the weak gravity conjecture can induce a phenomenologically viable value. The model predicts the existence of large extra dimensions compatible with observational constraints, and we note a possible connection with the dark dimension proposal.

The dark dimension in a warped throat

By combining swampland conjectures with observational data, it was suggested that our universe should lie in an asymptotic region of the quantum gravity landscape. The generalized distance conjecture for dS, the smallness of the cosmological constant and astrophysical constraints led to a scenario with one mesoscopic large dimension of size ℓ∼Λ−1/4∼10−6 m. We point out that a strongly warped throat with its redshifted KK tower provides a natural string theoretic mechanism that realizes the scaling m∼Λα with the factor α=1/4, the dark dimension being the one along the throat. We point out that in string theory it could be challenging to keep other KK towers heavy enough to avoid a conflict with astrophysical constraints on the number of extra large dimensions.

Extra dimensions with light and heavy neutral leptons: an application to CEνNS

We explore the possibility of relating extra dimensions with light and heavy Dirac-type neutral leptons and develop a framework for testing them in various laboratory experiments. The Kaluza-Klein modes in the large extra dimension models of the light neutral leptons could mix with the standard model neutrinos and produce observable effects in the oscillation experiments. We show that the chirality flipping up-scattering processes occurring through either neutrino magnetic dipole moment or the weakly coupled scalar interactions can also produce heavy Kaluza-Klein modes of the corresponding right-handed neutral leptons propagating in one or more extra dimensions. However, to conserve the four- dimensional energy-momentum, their masses must be below the maximum energy of the neutrinos in the initial state. The appreciable size of extra dimensions connected with these heavy neutral leptons can thus affect the cross-sections of these processes. This framework applies to any up-scattering process. Our work here focuses only on its application to the coherent elastic neutrino-nucleus scattering process. We derive constraints on the size of extra dimensions using the COHERENT data in oscillation and up-scattering processes. For model with one large extra dimension for the light neutral leptons, we obtain the limits, R ~ 3 μm (NH) and R ~ 2.5 μm (IH), on the size of extra dimension corresponding to the absolute mass limit, m0 ≤ 3 × 10−3 eV at 90% C.L. from the short-baseline oscillations. Using the up-scattering process for heavy neutral leptons, we obtain new parameter spaces between the size of extra dimensions and parameters of the dipole or scalar interactions.

Large extra dimensions and neutrino experiments

The existence of large extra dimensions can be probed in various neutrino experiments. We analyze several neutrino datasets in a model with a dominant large extra dimension. We show that the gallium anomaly can be explained with neutrino oscillations induced by the large extra dimension, but the region of parameter space that is preferred by the gallium anomaly is in tension with the bounds from reactor rate data, as well as the data of Daya Bay and MINOS. We also present bounds obtained from the analysis of the KATRIN data. We show that current experiments can put strong bounds on the size ${R}_{\mathrm{ED}}$ of the extra dimension: ${R}_{\mathrm{ED}}<0.20\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ and ${R}_{\mathrm{ED}}<0.10\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ at 90% C.L. for normal and inverted ordering of the standard neutrino masses, respectively.

Primordial black hole dark matter in the context of extra dimensions

Theories of large extra dimensions (LEDs) such as the Arkani-Hamed, Dimopoulos & Dvali scenario predict a "true" Planck scale $M_\star$ near the TeV scale, while the observed $M_{pl}$ is due to the geometric effect of compact extra dimensions. These theories allow for the creation of primordial black holes (PBHs) in the early Universe, from the collisional formation and subsequent accretion of black holes in the high-temperature plasma, leading to a novel cold dark matter (sub)component. Because of their existence in a higher-dimensional space, the usual relationship between mass, radius and temperature is modified, leading to distinct behaviour with respect to their 4-dimensional counterparts. Here, we derive the cosmological creation and evolution of such PBH candidates, including the greybody factors describing their evaporation, and obtain limits on LED PBHs from direct observation of evaporation products, effects on big bang nucleosynthesis, and the cosmic microwave background angular power spectrum. Our limits cover scenarios of 2 to 6 extra dimensions, and PBH masses ranging from 10 to $10^{21}$ g. We find that for two extra dimensions, LED PBHs represent a viable dark matter candidate with a range of possible black hole masses between $10^{17}$ and $10^{23}$ g depending on the Planck scale and reheating temperature. For $M_\star = 10$ TeV, this corresponds to PBH dark matter with a mass of $M \simeq 10^{21}$ g, unconstrained by current observations. We further refine and update constraints on "ordinary" four-dimension black holes.

Short-baseline oscillation scenarios at JUNO and TAO

We study the sensitivity of JUNO and TAO to the oscillations induced by two well-motivated scenarios beyond the standard model: large extra dimensions (LEDs) and light sterile neutrinos in the context of $3+1$ neutrino mixing. We find that $\mathrm{JUNO}+\mathrm{TAO}$ can set competitive bounds on the parameter space of each scenario. In particular, we find that $\mathrm{JUNO}+\mathrm{TAO}$ can be competitive with MINOS, DUNE, or KATRIN in the context of LED. If LEDs are present in nature, we show that the parameters could be measured with a similar precision as the standard oscillation parameters. We also show that $\mathrm{JUNO}+\mathrm{TAO}$ can test nearly all of the parameter space preferred by gallium experiments in the context of $3+1$ mixing. Finally, we discuss the possibility to distinguish the two scenarios from each other.

Neutrino condensate dark energy from TeV scale extra dimensions

We propose a new scenario of incorporating neutrino masses in models of TeV scale gravity and large extra dimensions, which can explain the dark energy problem through formation of neutrino condensates. The smallness of the neutrino masses and the scale of dark energy is protected to be small by the lepton number symmetry, which is broken in a distant brane, such that all lepton number violating effects are suppressed by the distance factor in the extra dimensions. The interactions of any bulk scalar particles are also suppressed by the distance factor. A lepton number violating soft-term is also induced from the distant brane, providing us a light pseudo-Nambu-Goldstone boson, which becomes the mediator of the attractive force that forms the condensates.