Effects Of Extra Dimensions Research Articles

Relativistic anisotropic star and its maximum mass in higher dimensions

We present a class of relativistic solutions of cold compact anisotropic stars in hydrostatic equilibrium in the framework of higher dimensions using spheroidal geometry. The solutions obtained with Vaidya-Tikekar metric are used to construct stellar models of compact objects and studied their physical features. The effects of anisotropy and extra dimensions on the global properties namely, compactness, mass, radius, equation of state are determined in higher dimensions in terms of the spheroidicity parameter (λ). It is noted that for a given configuration, compactness of a star is found smaller in higher dimensions compared to that in four space-time dimensions. It is also noted that the maximum mass of compact objects increase with the increase of space-time dimensions which however attains a maximum when D=5 for a large (λ=100), thereafter it decreases as one increases number of extra dimensions. The effect of extra dimensions on anisotropy is also studied.

Large extra dimension effects through light-by-light scattering at the CERN LHC

Observing light-by-light scattering at the large hadron collider (LHC) has received quite some attention and it is believed to be a clean and sensitive channel to possible new physics. In this paper, we study the diphoton production at the LHC via the process \({{pp}}\rightarrow {{p}}\gamma \gamma {{p}}\rightarrow {{p}}\gamma \gamma {{p}}\) through graviton exchange in the large extra dimension (LED) model. Typically, when we do the background analysis, we also study the double Pomeron exchange of \(\gamma \gamma \) production. We compare its production in the quark–quark collision mode to the gluon–gluon collision mode and find that contributions from the gluon–gluon collision mode are comparable to the quark–quark one. Our result shows, for extra dimension \(\delta =4\), with an integrated luminosity \(\mathcal{L} = 200\,\mathrm{fb}^{-1}\) at the 14 TeV LHC, that diphoton production through graviton exchange can probe the LED effects up to the scale \({M}_{S}=5.06 (4.51, 5.11)\,\mathrm{TeV}\) for the forward detector acceptance \(\xi _1 (\xi _2, \xi _3)\), respectively, where \(0.0015<\xi _1<0.5\), \(0.1<\xi _2<0.5\), and \(0.0015<\xi _3<0.15\).

Probe of extra dimensions inγq→γqat the LHC

We have examined TeV scale effects of extra spatial dimensions through the processes gamma q-> gamma q where q=u,d,c,s,b, anti-u, anti-d, anti-c, anti-s, anti-b. These processes have been treated in a photon-proton collision via the main reaction pp-> p gamma p-> p gamma qX at the LHC. We have employed equivalent photon approximation for incoming photon beams and performed statistical analysis for various forward detector acceptances.

TeV scale leptogenesis in [formula omitted] model with alternative cosmologies

In TeV scale B−L extension of the standard model with inverse seesaw, the Yukawa coupling of right-handed neutrinos can be of order one. This implies that the out-of-equilibrium condition for leptogenesis within the standard cosmology is not satisfied. We provide two scenarios for overcoming this problem and generating the desired value of the baryon asymmetry of the Universe. The first scenario is based on the extra-dimensional braneworld effects that modify the Friedman equation. We show that in this case the value of the baryon asymmetry of the Universe constrains the five-dimensional Planck mass to be of order 100 TeV. In the second scenario a non-thermal right-handed neutrino produced by the decay of a heavy moduli is assumed. In this case, we emphasize that it is possible to generate the required baryon asymmetry of the Universe for TeV scale right-handed neutrinos.

The model of the closed Universe with relativistic effects of extra dimension

The model of the closed Universe with relativistic effects of extra dimension

The Standard Model with one universal extra dimension

Effects of universal extra dimensions on Standard Model observables first arise at the one-loop level. The quantization of this class of theories is therefore essential in order to perform predictions. A comprehensive study of the SU C(3) × SU L(2) × U Y(1) Standard Model defined in a space-time manifold with one universal extra dimension, compactified on the oribifold \(S^1/Z_2\), is presented. The fact that the four-dimensional Kaluza–Klein theory is subjected to two types of gauge transformations is stressed and its quantization under the basis of the BRST symmetry discussed. A SU C(3) × SU L(2) × U Y(1)-covariant gauge-fixing procedure for the Kaluza–Klein excitations is introduced. The connection between gauge and mass eigenstate fields is established in an exact way. An exhaustive list of the explicit expressions for all physical couplings induced by the Yang–Mills, Currents, Higgs, and Yukawa sectors is presented. The one-loop renormalizability of the standard Green’s functions, which implies that the Standard Model observables do not depend on a cut-off scale, is stressed.

Cosmic strings with twisted magnetic flux lines and wound-strings in extra dimensions

We consider a generalization of the Nielsen-Olesen ansatz, in the abelian-Higgs model, which describes strings with twisted magnetic flux lines in the vortex core. The solution does not possess cylindrical symmetry, which leads to the existence of components of conserved momentum, both around the core-axis and along the length of the string. In addition, we consider a model of F-strings with rotating, geodesic windings in the compact space of the Klebanov-Strassler geometry and determine matching conditions which ensure energy and momentum conservation when loops chop off from the long-string network. We find that the expressions for the constants of motion, which determine the macroscopic string dynamics, can be made to coincide with those for the twisted flux line string, suggesting that extra-dimensional effects for F-strings may be mimicked by field-theoretic structure in topological defects.

Modified amplitude of the gravitational wave spectrum

The spectrum of thermal gravitational waves is obtained by including the high-frequency thermal gravitons created from extra-dimensional effects and is a new feature of the spectrum. The amplitude and spectral energy density of gravitational waves in a thermal vacuum state are found to be enhanced. The amplitude of the waves is modified in the frequency range (10−16–108 Hz) but the corresponding spectral energy density is less than the upper bound of various estimated results. With the addition of higher frequency thermal waves, the obtained spectral energy density of the wave in the thermal vacuum state does not exceed the upper bound put by the nucleosynthesis rate. The existence of cosmologically originated thermal gravitational waves due to extra dimension is not ruled out.

Revisiting the large extra dimension effects onW-pair production at the LHC in next-to-leading order QCD

In the framework of the large extra dimensions (LED) model, we investigate the effects induced by the Kaluza-Klein (KK) gravitons up to the QCD next-to-leading order (NLO) on the $W$-pair production followed by a subsequential $W$-decay at the CERN LHC. We depict the regions in the $\mathcal{L}-M_{S}$ parameter space where the LED effect can and cannot be observed from the analyses of the $pp \to W^+W^- + X$ and $pp \to W^+W^- \to W^{\pm}l^{\mp}\stackrel{(-)}{\nu} + X$ processes. We find that the ability of probing the LED effects can be improved by taking the cutoffs for the invariant mass of $W$-pair and the transverse momentum of the final lepton. Our results demonstrate that the NLO QCD corrections to observables are significant, and do not show any improvement for the renormalization/factorization scale uncertainty on the QCD NLO corrected cross section, because the LO result underestimates the scale dependence.

3D black holes on a 2-brane in 4D Minkowski space

We investigate three-dimensional black hole solutions in the realm of pure and new massive gravity in 2+1 dimensions induced on a 2-brane embedded in a flat four-dimensional spacetime. There is no cosmological constant neither on the brane nor on the four-dimensional bulk. Only gravitational fields are turned on and we indeed find vacuum solutions as black holes in 2+1 dimensions even in the absence of any cosmological solution. There is a crossover scale that controls how far the three- or four-dimensional gravity manifests on the 2-brane. Our solutions also indicate that local BTZ and SdS3 solutions can flow to local four-dimensional Schwarzschild-like black holes, as one probes from small to large distances, which is clearly a higher dimensional manifestation on the 2-brane. This is similar to the DGP scenario where the effects of extra dimensions for large probed distances along the brane manifest.

WHIZARD—simulating multi-particle processes at LHC and ILC

We describe the universal Monte-Carlo event generator WHIZARD. The program automatically computes complete tree-level matrix elements, integrates them over phase space, evaluates distributions of observables, and generates unweighted event samples that can be used directly in detector simulation. There is no principal limit on the process complexity; using current hardware, the program has successfully been applied to hard scattering processes with up to eight particles in the final state. Matrix elements are computed as helicity amplitudes, so spin and color correlations are retained. The Standard Model, the MSSM, and many alternative models such as Little Higgs, anomalous couplings, or effects of extra dimensions or noncommutative SM extensions have been implemented. Using standard interfaces to PDF, beamstrahlung, parton shower and hadronization programs, WHIZARD generates complete physical events and covers physics at hadron, lepton, and photon colliders.

One-loop effects of extra dimensions on theWWγandWWZvertices

The one-loop contribution of the excited Kaluza-Klein (KK) modes of the $SU_L(2)$ gauge group on the off-shell $WW\gamma$ and $WWZ$ vertices is calculated in the context of a pure Yang-Mills theory in five dimensions and its phenomenological implications discussed. The use of a gauge-fixing procedure for the excited KK modes that is covariant under the standard gauge transformations of the $SU_L(2)$ group is stressed. A gauge-fixing term and the Faddeev-Popov ghost sector for the KK gauge modes that are separately invariant under the standard gauge transformations of $SU_L(2)$ are presented. It is shown that the one-loop contributions of the KK modes to the off-shell $WW\gamma$ and $WWZ$ vertices are free of ultraviolet divergences and well-behaved at high energies. It is found that for a size of the fifth dimension of $R^{-1}\sim 1TeV$, the one-loop contribution of the KK modes to these vertices is about one order of magnitude lower than the corresponding standard model radiative correction. This contribution is similar to the one estimated for new gauge bosons contributions in other contexts. Tree-level effects on these vertices induced by operators of higher canonical dimension are also investigated. It is found that these effects are lower than those generated at the one-loop order by the KK gauge modes.

The effect of extra dimensions on gravity wave bursts from cosmic string cusps

We explore the kinematical effect of having extra dimensionson the gravitational wave emission from cosmic strings.Additional dimensions both round off cusps, and reduce the probability of their formation.We recompute the gravitational wave burst, taking into accountthese two factors, and find a potentially significant dampingon the gravitational waves of the strings.

Effect of Extra Dimensions on Gravitational Waves from Cosmic Strings

We show how the motion of cosmic superstrings in extra dimensions can modify the gravitational wave signal from cusps. Additional dimensions both round off cusps, as well as reducing the probability of their formation, and thus give a significant dimension dependent damping of the gravitational waves. We look at the implication of this effect for LIGO and LISA, as well as commenting on more general frequency bands.

A modified holographic dark energy model with infrared infinite extra dimension(s)

We propose a modified holographic dark energy (MHDE) model with the Hubble scale as the infrared (IR) cutoff. Introducing the infinite extra dimension(s) at very large distance scale, we consider the black hole mass in higher dimensions as the ultraviolet cutoff. Thus, we can probe the effects of the IR infinite extra dimension(s). As a concrete example, we consider the Dvali–Gabadadze–Porrati (DGP) model and its generalization. We find that the DGP model is dual to the MHDE model in five dimensions, and the ΛCDM model is dual to the MHDE model in six dimensions. Fitting the MHDE model to the observational data, we obtain that Ωm0=0.269−0.027+0.030, Ωk0=0.003−0.012+0.011, and the number of the spatial dimensions is N=4.78−0.44+0.68. The best fit value of N implies that there might exist two IR infinite extra dimensions.

Heal the world: Avoiding the cosmic doomsday in the holographic dark energy model

The current observational data imply that the universe would end with a cosmic doomsday in the holographic dark energy model. However, unfortunately, the big-rip singularity will ruin the theoretical foundation of the holographic dark energy scenario. To rescue the holographic scenario of dark energy, we employ the braneworld cosmology and incorporate the extra-dimension effects into the holographic theory of dark energy. We find that such a mend could erase the big-rip singularity and leads to a de Sitter finale for the holographic cosmos. Therefore, in the holographic dark energy model, the extra-dimension recipe could heal the world.

THERMODYNAMICS AND EXTRA DIMENSIONS

We consider the effects of extra dimensions on the thermodynamics of classical ideal gases, Bose–Einstein gases and Fermi–Dirac gas. Assuming a q-dimensional torus for the extra dimensions, we compute the thermodynamic functions such as the equation of state, the average energy and the specific heat at constant volume for the three systems. We show that the corrections due to the extra dimensions are small, proportional to [Formula: see text].

Massive fermion emission from higher dimensional black holes

We study the effect of extra dimensions on the process of massive Dirac fermion emission in the spacetime of the ($4+n$)-dimensional black hole, by examining the Dirac operator in arbitrary spacetime dimension. We comment on both bulk and brane emissions and find the absorption cross section and luminosity of Hawking radiation in the low-energy approximation.

Finite temperature Casimir effect in spacetime with extra compactified dimensions

In this Letter, we derive the explicit exact formulas for the finite temperature Casimir force acting on a pair of parallel plates in the presence of extra compactified dimensions within the framework of Kaluza–Klein theory. Using the piston analysis, we show that at any temperature, the Casimir force due to massless scalar field with Dirichlet boundary conditions on the plates is always attractive and the effect of extra dimensions becomes stronger when the size or number of the extra dimensions increases. These properties are not affected by the explicit geometry and topology of the Kaluza–Klein space.

SUPERSYMMETRY VERSUS BLACK HOLES AT THE LHC

Supersymmetry and extra dimensions are the two most promising candidates for new physics at the TeV scale. Supersymmetric particles or extra-dimensional effects could soon be observed at the Large Hadron Collider. We propose a simple but effective method to discriminate the two models: the analysis of isolated leptons with high transverse momentum. Black hole events are simulated with the CATFISH black hole generator. Supersymmetry simulations use a combination of PYTHIA and ISAJET, the latter providing the mass spectrum. Our results show that the measure of the dilepton invariant mass provides a promising signature to differentiate supersymmetry and black hole events at the Large Hadron Collider. Analysis of event-shape variables and multilepton events complement and strengthen this conclusion.