Randall-Sundrum Research Articles

Investigating μ±μ−→μ±μ− collisions under the effect of scalar and vector unparticles in Randall–Sundrum model

A theoretical attempt is made to present the unparticles contribution to the muon processes [Formula: see text], in Standard Model (SM), Randall–Sundrum (RS) model and RS model with unparticles (RS([Formula: see text])) including scalar and vector unparticles. We evaluated the cross-sections versus the scattering angle [Formula: see text], the kinetic energy [Formula: see text] of the outgoing muon beams, the collision energy [Formula: see text], the scaling dimension [Formula: see text] and the energy scale [Formula: see text]. The numerical results show that the cross-sections of two processes in RS([Formula: see text]) are much larger than in SM. The [Formula: see text] and [Formula: see text] beams can be accelerated and collided, producing the outgoing [Formula: see text] and [Formula: see text] beams as final states with large kinetic energy to probe new physics effects. The total cross-sections depend strongly on the polarization conditions of incoming muon and anti-muon beams, the scaling dimension [Formula: see text] and the energy scale [Formula: see text]. The final states of the muon collisions also depend on [Formula: see text] of colliders and unparticles parameter: ([Formula: see text], [Formula: see text]) if unparticle physics included. The results subsequently lead to the unparticle contribution as propagator significantly larger than SM and Higgs–radion propagator. Hence, it would be worthwhile probing at the future colliders when the muons become the accelerating candidates in the collisions we restricted.

Note on warped compactification. Finite brane potentials and non-Hermiticity

We study radius stabilization in the Randall-Sundrum model without assuming any unnaturally large stabilizing scalar potential parameter at the boundary branes (γ) by the frequently used superpotential method. Employing a perturbative expansion in 1/γ2 and the backreaction parameter, we obtain approximate analytical expressions for the radion mass and wavefunction. We validate them through a dedicated numerical analysis, which solves the linearized coupled scalar and metric field equations exactly. It is observed that the radion mass decreases with decreasing γ. Below a critical value of γ, the radion becomes tachyonic, suggesting destabilization of the extra dimension. We also address the issue of non-Hermiticity of the differential operator that determines the radion and Kaluza-Klein (KK) mode wavefunctions in the finite γ limit. It is accomplished by finding an explicit form of the general scalar product that re-establishes the orthogonality in the KK decomposition.

Hybrid branes from split kinks

In this work, we investigate braneworld models generated by scalar fields in which one field has a split kink profile, in which a kink separates into two kinklike configurations. Our analysis covers models with two and three fields, examining the behavior of the most important quantities associated with the brane, such as the warp factor and the stability of the corresponding gravity sector. The results show that the brane is stable and supports a hybrid character, behaving as a thin and thick configuration.

Interstellar exploration: From science fiction to actual technology

The technology for even the most advanced missions in the solar system doesn't need advances in basic science. Traveling through the solar system can be described through what is called ‵hard science fiction’, i.e. science fiction strictly based on scientific knowledge. Interstellar exploration is a completely different matter. Robotic flyby missions to the nearest stars using nanoprobes can be performed using technologies based on known science, while anything beyond this requires advances which we don't know how to implement, or even we are not sure whether they are possible at all. The point applies not only to the technological aspects but even the scientific bases on which the relevant technologies may rest. The missions requiring less scientific-technological advances, are slow missions, like space arks (generation ships) or missions based on hibernation with travel times up to hundred years. To implement both, the uncertainties are more related to the advances in space medicine and biology than in propulsion and physics. The fastest travels allowed by the current interpretations of the relativity theory are relativistic missions in which the time contraction at speeds closing the speed of light is exploited to decrease the travel time for the astronauts, although the travel time seen by those who remain on Earth is close, in years, to the distance traveled expressed in light years. However, the energy required for this type of missions is large and grows drastically with the increase of time contraction.Faster than light travel, which seems to be possible following some interpretations of relativity involving either wormholes or some sort of warp drive, requires substantial advances in fundamental physics. A symptom of this is that the novels dealing with interstellar travels belong more to the space opera – which doesn't follow strict scientific credibility – than to the hard science fiction subgenre. No novel of this kind explains details about how the relevant machinery works, and even less scientifically realistic are the movies, TV series, and videogames of this kind. Moreover, to achieve a travel time allowing to reach distant star systems in reasonable times using warp drives, the authors of Star Trek had to resort to the Warp Factor which is essentially a nonlinear scale. This makes the requirements for FTL travel even more difficult to achieve.

Phase transition to RS: cool, not supercool

Motivated by the warped conifold compactification, we model the infrared (IR) dynamics of confining gauge theories in a Randall-Sundrum (RS)-like setup by modifying the stabilizing Goldberger-Wise (GW) potential so that it becomes large (in magnitude) in the IR and back-reacts on the geometry. We study the high-temperature phase by considering a black brane background in which we calculate the entropy and free energy of the strongly back-reacted solution. As with Buchel’s result for the conifold [1], we find a minimum temperature beyond which the black brane phase is thermodynamically unstable. In the context of a phase transition to the confining background, our results suggest that the amount of supercooling that the metastable black brane phase undergoes can be limited. It also suggests the first-order phase transition (and the associated gravitational waves from bubble collision) is not universal. Our results therefore have important phenomenological implications for early universe model building in these scenarios.

Gravity-matter sum rules in models with a single extra-dimension

We prove a set of sum rules needed for KK-graviton pair production from matter in orbifolded extra-dimensional models. The sum rules can be found in full generality by considering the properties of solutions to the Sturm-Liouville problem, which describes the wave functions and the masses of the KK-gravitons in four dimensions. They ensure cancellations in the amplitudes of the processes mentioned above which considerably reduce their growth with s in the high-energy limit. This protects extra-dimensional theories from the low-scale unitarity problems that plague other theories with massive spin-2 particles. We argue that such relations are valid for a broader category of models thus generalizing our previous results that were limited to the large μ limit of the Randall-Sundrum model.

Spin-2 universal minimal solutions on type IIA and IIB supergravity

In this paper, we consider the spin-2 field perturbations of four families of supergravity solutions. These include AdS5 and AdS7 backgrounds of type IIA as well as AdS4 and AdS6 backgrounds of Type IIB. As the main result, we show that, in all the cases, there is a solution given by a combination of the warp factors. We also find the respective mass spectra. We analyze the normalizability of the solutions and identify the superconformal multiplets dual to them.

Braneworld black holes with ModMax electrodynamics on the brane

In this study, we investigate ModMax electrodynamics localized within the Randall–Sundrum II and Dvali–Gabadadze–Porrati branes, deriving corresponding 3-brane spacetime solutions that conform to the effective Einstein equations in each specific scenario. We construct solutions for charged black holes within the effective Einstein equation framework in both braneworld scenarios. The examination explores the trajectories of charged objects in this spacetime, underscoring the significance of the nonlinear parameter. Our analysis uncovers the fact that, similar to the prior ModMax black hole investigation, the nonlinear parameter plays a pivotal role in suppressing the effective charge of the black hole, due to its definite positive value.

The dynamics of three-forms in thick branes

In this work, we investigate thick brane models with a single three-form field. We find novel solutions for thick braneworlds where only three-forms exist and interact gravitationally in the bulk, both with and without matter fields. We use an additional scalar field as proxy for the matter fields. As an initial study, we consider the results here in contrast to the single scalar field thick braneworld case. The properties of the specific three-form parameterisation limits the freedom we have to choose the form of the warp factor, leading to a closed system of equations with nontrivial yet unstable solutions. The stability of the gravitational sector for thick brane three-forms is investigated and the models are shown to be unstable against small perturbations of the metric, further indicating that three-forms cannot exist stably in thick braneworld settings.

Constancy of stabilized Randall-Sundrum model with respect to quantum corrections

In the Randall-Sundrum model stabilized with the help of the Goldberger-Wise scalar field, the lowest order vacuum quantum corrections to the energy-momentum tensor of the scalar and tensor fields are calculated. It is shown that the corresponding vacuum energy density of the fields in the bulk leads to the Casimir effect. Using the dimensional regularization method and the Abel-Plana formula, the divergences have been isolated and the vacuum energy density has been renormalized. An analytical expression for the Casimir force is obtained and an estimate of its influence on the model parameters is made. It was found that the quantum corrections lead only to a negligibly small decrease in the distance between the branes, i.e. the model possesses constancy with respect to quantum corrections.

Investigation of the scalar unparticle and anomalous couplings at muon colliders in final states with multiple photons in the Randall–Sundrum model

The influence of the scalar unparticle and anomalous couplings at muon colliders in final states with multiple photons in the Randall–Sundrum model is evaluated in detail. The results indicate that with fixed collision energies, the total cross-sections for the production of multiple photons depend strongly on the polarization of the muon beams, the parameters of unparticle physics (the scaling dimension [Formula: see text], operator [Formula: see text], the energy scale [Formula: see text]) and also the strength of anomalous couplings. Numerical evaluation shows that the cross-sections for the production of four photons in finale states with the contribution of scalar anomalous couplings are much larger than that of the unparticle under the same conditions. In the Higgs–radion mixing, the cross-sections achieve the maximum value at the radion-dominated state, [Formula: see text][Formula: see text]GeV, in which the cross-section is much enhanced and can be measurable in current experiments.

Heavy quarkonium spectral function in an anisotropic background

In this paper, we use a five-dimensional Einstein-dilaton-two-Maxwell holographic QCD model to investigate the dissociation effects of J/Ψ and ϒ(1S) states in an anisotropic medium by calculating their spectral functions. First, we present the holographic quarkonium masses at zero temperature via physics-informed neural networks. Then, at a finite temperature, we derive the spectral functions, representing heavy vector mesons as peaks, and observe that with increasing anisotropy, temperature, chemical potential, and warp factor, the peak height diminishes while its width expands, indicating an accelerated dissociation process. Additionally, the results indicate the anisotropy induces a stronger dissociation effect in the direction parallel to the polarization compared to the perpendicular, revealing the anisotropy’s directional influence. Published by the American Physical Society 2024

Steadiness of Stabilized Randall–Sundrum Model with Respect to Quantum Corrections

Steadiness of Stabilized Randall–Sundrum Model with Respect to Quantum Corrections

A novel model of non-singular oscillating cosmology on flat Randall–Sundrum II braneworld

A novel model of non-singular oscillating cosmology on flat Randall–Sundrum II braneworld

The Contribution of Photon, Z Boson, Higgs, Radion and Unparticle to the Processes in Randall-Sundrum Model

The fundamentally well-known process of Bhabha is studied from the theoretical view of unparticle physics in the prominent Randall-Sundrum model. The cross-sections independently for photon (γ), Z boson (Z), vector unparticle (Uμ), Higgs (h), radion (), and scalar unparticle (U) exchange are calculated and evaluated. Numerical calculations showed that the contribution of unparticle exchange dominates in very high energy regions. While the standard model exchanges as γ and Z are predominant in the lower energy region, h and contribution is very small in comparison with the other exchanges. The results are plotted in the energy ranges available in the present designs of accelerators and near future energy upgrades of the International Linear Collider (ILC) and The Compact Linear Collider (CLIC).

Y-algebroids and E7(7)× ℝ+-generalised geometry

We define the notion of Y-algebroids, generalising the Lie, Courant, and exceptional algebroids that have been used to capture the local symmetry structure of type II string theory and M-theory compactifications to D ≥ 5 dimensions. Instead of an invariant inner product, or its generalisation arising in exceptional algebroids, Y-algebroids are built around a specific type of tensor, denoted Y , that provides exactly the necessary properties to also describe compactifications to D = 4 dimensions. We classify “M-exact” E7-algebroids and show that this precisely matches the form of the generalised tangent space of E7(7) × ℝ+-generalised geometry, with possible twists due to 1-, 4- and 7-form fluxes, corresponding physically to the derivative of the warp factor and the M-theory fluxes. We translate the notion of generalised Leibniz parallelisable spaces, relevant to consistent truncations, into this language, where they are mapped to so-called exceptional Manin pairs. We also show how to understand Poisson-Lie U-duality and exceptional complex structures using Y-algebroids.

Search for quantum black hole production in lepton+jet final states using proton-proton collisions at s=13 TeV with the ATLAS detector

A search for quantum black holes in electron+jet and muon+jet invariant mass spectra is performed with 140 fb−1 of data collected by the ATLAS detector in proton-proton collisions at s=13 TeV at the Large Hadron Collider. The observed invariant mass spectrum of lepton+jet pairs is consistent with Standard Model expectations. Upper limits are set at 95% confidence level on the production cross section times branching fractions for quantum black holes decaying into a lepton and a quark in a search region with invariant mass above 2.0 TeV. The resulting quantum black hole lower mass threshold limit is 9.2 TeV in the Arkani-Hamed-Dimopoulos-Dvali model, and 6.8 TeV in the Randall-Sundrum model. © 2024 CERN, for the ATLAS Collaboration 2024 CERN

De Sitter Versus Anti‐de Sitter in Horndeski‐Like Gravity

AbstractThe general solutions of Horndeski‐like gravity that can interpolate between the de Sitter and anti‐de Sitter regimes are presented. In particular, the first‐order formalism with two scalar fields is developed, and considering a black hole ansatz with flat slicing, three different cases, namely exponential, vacuum, and smooth superpotential solutions, with no Minkowski extrema are investigated. Furthermore, these solutions show that a Renormalization Group flow is established, and a turnaround in the warp factor is obtained, where the transition is bounded by the area low. The ideal regimes to trap gravity, which are constructed using the holographic function, which provides stable and unstable regimes to localize gravity are discussed. Finally, it is shown that no ghost appear and that the matter sector that violates the ‐theorem is physical.

Quantum gravity induced entanglement of masses with extra dimensions

It is believed that gravity can be considered as a quantum coherent mediator. In this study, we propose a plan to test the existence of extra dimensions using the quantum gravity induced entanglement of masses (QGEM) experiment. This experiment involves two freely falling test masses passing through a Stern–Gerlach-like device. We investigate the entanglement witness between these masses within the framework of the Randall–Sundrum II model (RS-II). Our findings indicate that the system reaches entanglement more rapidly in the presence of extra dimensions, particularly when the radius of the extra dimension is large.

Flat and bent branes in Born–Infeld-like scalar field models

In this work, we investigate the presence of thick branes modeled by a single scalar field with Born–Infeld-like dynamics. We consider the 4-dimensional metric being Minkowski, de Sitter or anti-de Sitter. We obtain the field equations and the conditions to get a first order formalism compatible with them. To illustrate our procedure, some specific models are presented. They support localized warp factor and have their properties controlled by the 4-dimensional cosmological constant. In particular, a hybrid brane may arise, with a thick or thin profile depending on the extra dimension being inside or outside a compact space.