The Little Randall-Sundrum (Little RS) model receives significantly stronger constraints from the flavour observables in comparison to Randall-Sundrum (RS) model. In this paper, we analyse the effect of the electro-weak sector in Little RS on flavour changing decays of charged leptons. We compare the predictions of the model with the current limits on the flavour violating Branching Ratios of $μ\rightarrow e e e $, $τ\rightarrow e e e $, $τ\rightarrow μμμ$, $τ\rightarrow μe e $, $τ\rightarrow e μμ$ , $μ\rightarrow e γ$, and $μTi \rightarrow e Ti $. And we show that the dominant constraint arises from the $μTi \rightarrow e Ti$ process which strongly limits the KK-1 gauge boson mass ($M_{KK}$) to be $\gtrsim 30.7 TeV $. We then derive and show that generalising the electro-weak gauge sector to include the Brane Localised Kinetic Term (BLKT) relaxes this constraint to $\gtrsim 12 TeV$. Towards the conclusion, we comment on the possibility that the large flavour violating currents can be mitigated by relaxing the assumption regarding the unnatural thinness and rigidity of the UV-brane and discuss the possibility of suppression of these currents in presence of fat fluctuating branes.
Considering the Randall-Sundrum background, we calculate the total cross-section for $ϕϕ^\star \to G γ$ in the framework of the scalar electrodynamics.
We compute the two-derivative low-energy effective action for the radion in the (supersymmetric) Randall-Sundrum scenario with detuned brane tensions. At the classical level, a potential automatically stabilizes the distance between the branes. In the supersymmetric case, supersymmetry can be broken spontaneously by a vacuum expectation value for the fifth component of the graviphoton.
We present a Randall-Sundrum toy model with an added scalar singlet that couples only to KK fermions in the bulk. Such a scalar would nontrivially affect radion phenomenology. In addition, we examine the radion phenomenology in light of the new scalar and show how this scalar could present another probe to search for the radion.
We investigate the spectroscopy of scalar and vector Kaluza-Klein modes that arise in a deformed Randall-Sundrum model that is constructed from Brans-Dicke theory. The non-minimal coupling in the Brans Dicke theory translates into a deformation of the Randall-Sundrum geometry that depends on the Brans-Dicke parameter $ω$. We find that the $ω$ parameter has a non-trivial effect in the spectroscopy of scalar and vector Kaluza-Klein modes. Our results suggest the interpretation of $ω$ as a fine-tuning parameter.
Unparticle behavior is shown to be realized in the Randall-Sundrum 2 (RS 2) and the Lykken-Randall (LR) brane scenarios when brane-localized Standard Model currents are coupled to a massive vector field living in the five-dimensional warped background of the RS 2 model. By the AdS/CFT dictionary these backgrounds exhibit certain properties of the unparticle CFT at large N_c and strong 't Hooft coupling. Within the RS 2 model we also examine and contrast in detail the scalar and vector position-space correlators at intermediate and large distances. Unitarity of brane-to-brane scattering amplitu…
Recursive relations from diffeomorphism in the Randall-Sundrum model
College of Physics and Communication Electronics, Jiangxi Normal University（江西师范大学物理与通信电子学院）；Laboratoire de Physique Theorique et Hautes Energies, UMR 7589, Sorbonne Université & CNRS（索邦大学与法国国家科学研究中心理论物理与高能物理联合实验室）
We construct the second variation Lagrangian for Randall-Sundrum model with two branes, study its gauge invariance, find the corresponding equations of motion and decouple them. We also derive an effective Lagrangian for this model in the unitary gauge, which describes a massless graviton, massive gravitons and a massless scalar radion. It is shown that the mass spectra of these fields and their couplings to the matter are different on different branes.
The Kaluza-Klein theory and Randall-Sundrum theory are examined comparatively, with focus on the five dimensional (Dirac) fermion and the dimensional reduction to four dimensions. They are treated in the Cartan formalism. The chiral property, localization, anomaly phenomena are examined. The electric and magnetic dipole moment terms naturally appear. The order estimation of the couplings is done. This is a possible origin of the CP-violation.
Models with one warped and two unwarped extra dimensions allow for the solution of a number of open questions in particle physics. They can be used to solve the hierarchy problem in the same sense as Randall-Sundrum extra dimensions, they incorporate the Randall-Sundrum approach to flavor, and they generate a dark matter candidate via Kaluza-Klein parity in the flat extra dimensions. In this paper, we examine the models AdS_5 x T_2 and AdS_5 x S_2, deriving the Kaluza-Klein spectrum for fermions propagating in the bulk. While the toroidal model allows for a chiral zero mode, we find that the p…
We find renormalization group transformations for the compactified Randall-Sundrum scenario by integrating out an infinitesimal slice of ultraviolet degrees of freedom near the Planck brane. Under these transformations the coefficients of operators on the Planck brane experience RG evolution. The extra-dimensional radius also scales, flowing to zero in the IR. We find an attractive fixed point in the context of a bulk scalar field theory. Calculations are simplified in the low energy effective theory as we demonstrate with the computation of a loop diagram.
We modify Randall-Sundrum model of brane-world (with two branes) by adding the scalar curvature squared term in five dimensions. We find that it does not destabilize Randall-Sundrum solution to the hierarchy problem of the Standard Model in particle physics.
We study the problem of integrating an invisible axion into the Randall-Sundrum scenario as an example of how to generate new energy scales between the extremes of the Planck mass and the electroweak scale. In this scenario, the axion corresponds to the phase of complex bulk scalar field. We show how to generate an intermediate energy scale by including a third brane in the scenario. We discuss the stabilization of this brane in detail to demonstrate that no additional fine-tunings arise.
We discuss some issues about the holographic interpretation of the compact Randall-Sundrum model, which is conjectured to be dual to a 4d field theory with non-linearly realized conformal symmetry. We make several checks of this conjecture. In particular, we show that the radion couples conformally to a background 4d metric. We also discuss the interpretation of the Goldberger-Wise mechanism for stabilizing the radion. We consider situations where the electroweak breaking stabilizes the radion and we discuss the issue of natural conservation of flavor quantum numbers.
It has been proposed that Randall-Sundrum models can be holographically described by a regularized (broken) conformal field theory. We analyze the foundations of this duality using a regularized version of the AdS/CFT correspondence. We compare two- and three-point correlation functions and find the same behaviour in both descriptions. In particular, we show that the regularization of the deformed CFT generates kinetic terms for the sources, which hence can be naturally treated as dynamical fields. We also discuss the counterterms required for two- and three-point correlators in the renormaliz…
We evaluate the Casimir force between two parallel plates in Randall Sundrum (RS) scenarios extended by q compact dimensions. After giving exact expressions for one extra compact dimension (RS 6D model), we generalize to an arbitrary number of compact dimensions. We present the complete calculation for both two brane scenario (RSI model) and one brane scenario (RSII models) using the method of summing over the modes. We investigate the effects of extra dimensions on the magnitude and sign of the force, and comment on limits for the size and number of the extra dimensions.
A recent work has investigated the possibility that the mass scale for the ultraviolet (UV) brane in the Randall-Sundrum (RS) model is of the order 10^3 TeV. In this so called ``Little Randall-Sundrum'' (LRS) model the bounds on the gauge sector are less severe, permitting a lower Kaluza-Klein scale and cleaner discovery channels. However employing a low UV scale nullifies one major appeal of the RS model; namely the elegant explanation of the hierarchy between the Planck and weak scales. In this work we show that by localizing the gauge, fermion and scalar sector of the LRS model on a five di…
In this paper we discuss in detail a numerical method to study resonances in membranes generated by domain walls in Randall-Sundrum-like scenarios. It is based on similar works to understand the quantum mechanics of electrons subject to the potential barriers that exist in heterostructures in semiconductors. This method was used recently to study resonances of a three form field and lately generalized to arbitrary forms. We apply it to a lot of important models, namely those that contain the Gauge, Gravity and Spinor fields. In many cases we find a rich structure of resonances which depends on…
We consider a Randall-Sundrum model in which the Standard Model fermions and gauge bosons correspond to bulk fields. We show how the observed charged fermion masses and CKM mixings can be explained, without introducing hierarchical Yukawa couplings. We then study the impact on the mass scales associated with non-renormalizable operators responsible for proton decay, neutrino masses, and flavor changing neutral currents. Although mass scales as high as 10^{11}- 10^{12} GeV are in principle possible, dimensionless couplings of order 10^{-8} are still needed to adequately suppress proton decay. L…
The generalization of the Randall-Sundrum solution for the warp factor exp[sigma(y)] in the scenario with one extra coordinate y, non-factorizable space-time geometry and two branes isobtained. It is shown that the function obtained sigma(y) is symmetric with respect to an interchange of two branes. It also obeys the orbifold symmetry y -> - y and explicitly reproduces jumps of its derivative on both branes. This solution is defined by the Einstein-Hilbert's equations up to a constant C. It is demonstrated that different values of C results in theories with quite different spectra of the Kaluz…
An approach to find the field equation solution of the Randall-Sundrum model with the $S^1/Z_2$ extra axis is presented. We closely examine the infrared singularity. The vacuum is set by the 5 dimensional Higgs field. Both the domain-wall and the anti-domain-wall naturally appear, at the {\it ends} of the extra compact axis, by taking a {\it new infrared regularization}. The stability is guaranteed from the outset by the kink boundary condition. A {\it continuous} (infrared-)regularized solution, which is a truncated {\it Fourier series} of a {\it discontinuous} solution, is utilized.The ultra…
We suggest a modification of the Randall-Sundrum scenario which doesn't involve branes with the negative tensions. In our scenario four-dimensional brane world is produced by the external field. The probability of this process is calculated and the physical features of the model are discussed.
The asymptotic behavior of metric perturbations in Randall-Sundrum infinite brane world is carefully investigated. Perturbations generated by matter fields on the brane are shown to be regular even at the future Cauchy horizon.
In the generalized Randall-Sundrum warped brane-world model the cosmological constant induced on the visible brane can be positive or negative. In this paper we investigate profiles of vacuum expectation value of the bulk scalar field under general Dirichlet andNeumann boundary conditions in the generalized warped brane-worldmodel.We showthat the VEVprofiles generally depend on the value of the brane cosmological constant. We find that the VEV profiles of the bulk scalar field for a visible brane with negative cosmological constant and positive tension are quite distinct fromthose of Randall-S…
We derive the second variation Lagrangian of the Randall-Sundrum model with two branes, study its gauge invariance and diagonalize it in the unitary gauge. We also show that the effective four-dimensional theory looks different on different branes and calculate the observable mass spectra and the couplings of the physical degrees of freedom of 5-dimensional gravity to matter.
The physics of the Randall-Sundrum model relevant for future linear colliders is briefly summarized. The differences between the case where Standard Model(SM) fields are on the wall and where they are in the bulk are emphasized.
The spin-2 graviton excitations in the Randall-Sundrum gravity model provides a t-channel contribution to electron Compton scattering which competes favourably with the standard QED contributions. The phenomenological implications of these contributions to the unpolarized and polarized cross-sections are evaluated.
We study the process $e^- e^- \to e^- e^-$ at a high energy $e^- e^-$ collider including the effect of graviton exchanges in the warped gravity model of Randall and Sundrum. Discovery limits for gravitons are established and the effects of polarization are discussed.
Bulk antisymmetric tensor fields of different ranks have been studied in the context of a generalized Randall-Sundrum model with a non-vanishing induced cosmological constant on the visible brane. It is shown that instead of the usual exponential suppression of the couplings of the zero modes of these bulk fields with the brane fermions in the original Randal-Sundrum model, here the couplings are proportional to the brane cosmological constant. Thus in an era of large cosmological constant these fields have significant role in physical phenomena because of their enhanced couplings with the vis…
We study polarized cross-sections and forward-backward asymmetry for the process $e^+e-\to τ^+τ^-$ in the stabilized Randall-Sundrum scenario. It is shown that there is substantial deviation from the Standard Model predictions, both in terms of the actual numerical values and angular distributions.
We discuss several methods which can be used to distinguish the graviton resonances of the Randall-Sundrum model from the graviton-like resonances which may occur in other theories. The Breit-Wigner line shape of the RS graviton is found to be particularly useful. In particular we show that the "effective" graviton resonance present in the model of Dvali et al ~can be distinguished from those of the Randall-Sundrum scenario for a reasonably wide range of model parameters.
We obtain the general inflationary solutions for the slab of five-dimensional AdS spacetime where the fifth dimension is an orbifold $S^1/Z_2$ and two three-branes reside at its boundaries, of which the Randall-Sundrum model corresponds to the static limit. The investigation of the general solutions and their static limit reveals that the RS model recasts both the cosmological constant problem and the gauge hierarchy problem into the balancing problem of the bulk and the brane cosmological constants.
We show that when the antisymmetric Kalb-Ramond field is included in the Randall-Sundrum scenario, although the hierarchy problem can be solved, it requires an extreme fine tuning of the Kalb-Ramond field (about 1 part in $10^{62}$). We interpret this as the return of the problem in disguise. Further, we show that the Kalb-Ramond field induces a small negative cosmological constant on the visible brane.
The extremely small branching ratio of $b\to ss{\bar d}$ decay in the Standard Model makes it a suitable channel to explore new-physics signals. We study this $ΔS=2$ process in Randall-Sundrum models, including the custodially protected and the bulk-Higgs Randall-Sundrum models. Exploring the experimentally favored parameter spaces of these models, it suggests a possible enhancement of the decay rate, compared to the Standard Model result, by at most two orders of magnitude.
We observe that the main feature of the Randall-Sundrum model, used to solve the hierarchy problem, is already present in a class of Yang-Mills plus gravity theories inspired by noncommutative geometry. Strikingly the same expression for the Higgs potential is found in two models which have no apparent connection. Some speculations concerning the possible relationships are given.
The effective gravitational interaction below the Planck scale in the Randall-Sundrum world is shown to be the Gauss-Bonnet term. In this theory we find that there exists another static solution with a positive bulk cosmological constant. Also, there exist solutions for positive visible sector cosmological constant, which are needed for a later Friedman-Robertson-Walker universe.
The cosmology of a brane-universe embedded in a higher dimensional bulk spacetime presents some peculiarities not seen in ordinary (3+1) dimensional gravity. I summarize the current understanding, with emphasis on the suggestion by Randall and Sundrum that the bulk is 5-D anti-deSitter space, leading to a solution of the weak scale hierarchy problem.
In the search for extra dimension through dilepton events in 7-TeV proton-proton collision, the ATLAS detector at LHC has set stringent lower bound on the mass of the Randall-Sundrum (RS) lightest graviton Kaluza-Klein (KK) mode. Considering that the Randall-Sundrum model undertakes to resolve the well-known gauge hierarchy/fine tuning problem to restrict the Higgs mass within the estimated $\sim 126$ GeV against large radiative correction upto the cut-off of the model, we explore the allowed parameter space within which the RS model can be trusted. We show that the consistency of the model wi…
We study the radiative lepton flavor violating l_i -> l_jγdecays in the two Higgs doublet model, respecting the Randall Sundrum scenario and estimate the contributions of the KK modes of left (right) handed charged lepton doublets (singlets) on the branching ratios. We observe that the branching ratios are sensitive to the contributions of the charged lepton KK modes.
In this talk I describe the low energy effective theory of the (supersymmetric) Randall-Sundrum scenario with arbitrary brane tensions. The distance between the branes is stabilized, at the classical level, by a potential for the radion field. In the supersymmetric case, supersymmetry can be broken by a VEV for the fifth-component of the graviphoton.
We revive an old result, that one-loop corrections to the graviton propagator induce 1/r^3 corrections to the Newtonian gravitational potential, and compute the coefficient due to closed loops of the U(N) {\cal N}=4 super-Yang-Mills theory that arises in Maldacena's AdS/CFT correspondence. We find exact agreement with the coefficient appearing in the Randall-Sundrum brane-world proposal. This provides more evidence for the complementarity of the two pictures.
Chern-Simons AdS supergravity theories are gauge theories for the super-AdS group. These theories possess a fermionic symmetry which differs from standard supersymmetry. In this paper, we study five-dimensional Chern-Simons AdS supergravity in a Randall-Sundrum scenario with two Minkowski 3-branes. After making modifications to the D = 5 Chern-Simons AdS supergravity action and fermionic symmetry transformations, we obtain a Z_2-invariant total action S = \tilde{S}_bulk + S_brane and fermionic transformations \tildeδ_ε. While \tildeδ_ε\tilde{S}_bulk = 0, the fermionic symmetry is broken by S_b…
A detailed phenomenological analysis of neutral kaon mixing in "little Randall-Sundrum" models is presented. It is shown that the constraints arising from the CP-violating quantity epsilon_K can, depending on the value of the ultra-violet cutoff, be even stronger than in the original Randall-Sundrum scenario addressing the hierarchy problem up to the Planck scale. The origin of the enhancement is explained, and a bound Lambda_{UV}>several 10^3 TeV is derived, below which vast corrections to epsilon_K are generically unavoidable. Implications for non-standard Z->bb couplings are briefly discuss…
A generalized version of the Randall-Sundrum model-2 with different cosmological constants on each side of a brane has been discussed. A possibility of replacing the singular brane by a configuration of a scalar field has been also considered, the Einstein equations for this setup were solved and stability of the solution discussed. It has been shown that under mild assumptions the relation between cosmological constants and the brane tension obtained in the brane limit does not depend on the particular choice of the regularizing profile of the scalar field.
In the Randall-Sundrum model there can be a rich new phenomenology associated with Higgs-radion mixing. A photon-photon collider would provide a crucial complement to the LHC and a future ILC collider for fully determining the parameters of the model and definitively testing it.
In the Randall-Sundrum solution to the hierarchy problem, the fluctuations of the size of the extra dimension are characterized by a single scalar field, called the radion. The radion is expected to have a mass somewhat lower than the TeV scale with couplings of order 1/TeV to the trace of the energy momentum tensor. In addition, the radion can mix with the Higgs boson. Implications for phenomenology are briefly reviewed.
We study the charged lepton electric dipole moments in the Randall Sundrum model where the leptons and the gauge fields are accessible to the extra dimension. We observe that the electron (muon; tau) electric dipole moment reaches to the value of the order of 10^{-26} e-cm (10^{-20} e-cm; 10^{-20} e-cm) with the inclusion of the lepton KK modes.
Recently proposed stabilization mechanism of the Randall-Sundrum metric gives rise to a scalar radion, which couples universally to matter with a weak interaction ($\simeq 1$ TeV) scale. Demanding that gauge boson scattering as described by the effective low enerrgy theory be unitary upto a given scale leads to significant constraints on the mass of such a radion.
We provide the first complete analysis of cosmological evolution in the Randall-Sundrum model with stabilized dilaton. We give the exact expansion law for matter densities on the two branes with arbitrary equations of state. The effective four-dimensional theory leads to standard cosmology at low energy. The limit of validity of the low energy theory and possible deviations from the ordinary expansion law in the high energy regime are finally discussed.
In the context of an inflationary Randall-Sundrum Type II braneworld (RS2) we calculate spectral indices and amplitudes of cosmological scalar and tensor perturbations, up to second order in slow-roll parameters. Under very simple assumptions, extrapolating next-order formulae from first-order calculations in the case of a de Sitter brane, we see that the degeneracy between standard and braneworld lowest-order consistency equations is broken, thus giving different signatures of early-universe inflationary expansion. Using the latest results from WMAP for estimates of cosmological observables, …
We extend the Randall-Sundrum(RS) model by adding a fundamental scalar field in the bulk, then study the multi-field assisted inflationary solution on brane. We will show that this model satisfies not only the observation, but also provides a solution to hierarchy problem. Furthermore in comparison with the chaotic inflation model with a single field in four space-time dimension, the parameters in our model required for a successful inflation are natural.
The brief review of the recent results obtained in the Randall-Sundrum scenario with the small curvature of the five-dimensional space-time is presented.
We study 5D gauge symmetries in the Randall-Sundrum geometry that are hidden from the standard model through either small 5D gauge coupling, or through vanishing quantum numbers for the standard model fields. Geometric warping of 5D gravity creates a TeV scale bridge from the standard model to the hidden sector gauge fields. We apply these concepts to a revival of the electroweak axion model, in which the dynamics of Peccei-Quinn symmetry breaking occur at the TeV scale.
We discuss the semiclassical instability of the Randall-Sundrum brane-world model against a creation of a kind of Kaluza-Klein bubble. An example describing such a bubble space-time is constructed from the five-dimensional AdS-Schwarzschild metric. The induced geometry of the brane looks like the Einstein-Rosen bridge, which connects the positive and the negative tension branes. The bubble rapidly expands and there also form a trapped region around it.
We consider a string-inspired torsion-dilaton-gravity action in a Randall-Sundrum brane world scenario and show that, in an effective four-dimensional theory on the visible brane, the rank-2 antisymmetric Kalb-Ramond field (source of torsion) is exponentially suppressed. The result is similar to our earlier result in [12], where no dilaton was present in the bulk. This offers an explanation of the apparent invisibility of torsion in our space-time. However, in this case the trilinear couplings ~ Tev^{-1} between dilaton and torsion may lead to new signals in Tev scale experiments, bearing the …
In the framework of Randall-Sundrum model, we discuss the evolution of microscopic black holes created by cosmic particles hitting a neutron or a strange star. We set up the general equations of evolution for the black hole mass and momentum in a dense medium, and discuss the possibility of collapse due to the black hole's growth inside the star.
I present phenomenological implications of the Randall-Sundrum model for indirect searches, specifically a selection of flavor observables and Higgs-related collider searches. I review the interplay of constraints from CP violation in flavor physics, possible effects in rare decays, and model-specific protection mechanisms. Deviations in the Higgs couplings to fermions and, at one-loop, to gluons are unexpectedly strong and lead to strong modifications in Higgs searches.
The Randall-Sundrum model with gauge fields and fermions in the bulk has several attractive features including the gauge coupling unification, a candidate for the dark matter, and an explanation for the hierarchical Yukawa couplings. In this paper, we point out that the 1st Kaluza-Klein modes of right-handed neutrinos may be produced at colliders, for both Dirac and Majorana neutrino cases. Furthermore, we can see whether the neutrino masses are Dirac type or Majorana type from the mass spectrum of KK particles.
