Presence Of Extra Dimensions Research Articles

SEMITRANSPARENT PISTONS

We consider semitransparent pistons in the presence of extra dimensions. It is shown that the piston is always attracted to the closest wall irrespective of details of the geometry and topology of the extra dimensions and of the cross section of the piston. Furthermore, we evaluate the zeta regularized determinant for this configuration.

IS DARK MATTER AN EXTRA-DIMENSIONAL EFFECT?

We investigate the possibility that the observed behavior of test particles outside galaxies, which is usually explained by assuming the presence of dark matter, is the result of the dynamical evolution of particles in higher dimensional spacetimes. Hence, dark matter may be a direct consequence of the presence of an extra force, generated by the presence of extra dimensions, which modifies the dynamic law of motion, but does not change the intrinsic properties of the particles, like, for example, the mass (inertia). We discuss in some detail several possible particular forms for the extra force, and the acceleration law of the particles is derived. Therefore, the constancy of the galactic rotation curves may be considered as an empirical evidence for the existence of the extra dimensions.

APOLLO: A NEW PUSH IN LUNAR LASER RANGING

APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) is a new effort in lunar laser ranging that uses the Apollo-landed retroreflector arrays to perform tests of gravitational physics. It achieved its first range return in October 2005, and began its science campaign the following spring. The strong signal (> 2500 photons in a ten-minute period) translates to one-millimeter random range uncertainty, constituting at least an order-of-magnitude gain over previous stations. One-millimeter range precision will translate into order-of-magnitude gains in our ability to test the weak and strong equivalence principles, the time rate of change of Newton's gravitational constant, the phenomenon of gravitomagnetism, the inverse-square law, and the possible presence of extra dimensions. An outline of the APOLLO apparatus and its initial performance is presented, as well as a brief discussion on future space technologies that can extend our knowledge of gravity by orders of magnitude.

Graviton emission from a Schwarzschild black hole in the presence of extra dimensions

In this talk I presented a previously published work concerning the evaporation of (4 + n)-dimensional non-rotating black holes into gravitons [Creek S, Efthimiou O, Kanti P and Tamvakis K 2006 Phys. Lett. B 635 39 (Preprint hep-th/0601126)]. In this work we calculated the energy emission rate for gravitons in the bulk obtaining analytical solutions of the master equation satisfied by all three types (S, V, T) of gravitational perturbations and presented graphs for the absorption probability and the energy emission of the black hole in the bulk.

On the 5D Extra-Force according to Basini–Capozziello–Ponce De Leon Formalism and five important features: Kar–Sinha Gravitational Bending of Light, Chung–Freese Superluminal Behaviour, Maartens–Clarkson Black Strings, experimental measures of Extra Dimensions on board International Space Station (ISS) and the existence of the Particle Z due to a higher dimensional spacetime

We use the Conformal Metric as described in Kar–Sinha work on Gravitational Bending of Light in a 5D Spacetime to recompute the equations of the 5D Force in Basini–Capozziello–Ponce De Leon Formalism and we arrive at a result that possesses some advantages. The equations of the Extra Force as proposed by Ponce De Leon are now more elegant in Conformal Formalism and many algebraic terms can be simplified or even suppressed. Also we recompute the Kar–Sinha Gravitational Bending of Light affected by the presence of the Extra Dimension and analyze the Superluminal Chung–Freese Features of this Formalism describing the advantages of the Chung–Freese BraneWorld when compared to other Superluminal spacetime metrics (e.g. Warp Drive) and we describe why the Extra Dimension is invisible and how the Extra Dimension could be made visible at least in theory. We also examine the Maartens–Clarkson Black Holes in 5D (Black Strings) coupled to massive Kaluza–Klein graviton modes predicted by Extra Dimensions theories and we study experimental detection of Extra Dimensions on-board LIGO and LISA Space Telescopes. We also propose the use of International Space Station (ISS) to measure the additional terms (resulting from the presence of Extra Dimensions) in the Kar–Sinha Gravitational Bending of Light in Outer Space to verify if we really lives in a Higher Dimensional Spacetime. Also we demonstrate that Particle Z can only exist if the 5D spacetime exists.

Gravitationally induced quantum superposition reduction with large extra dimensions

A gravity-driven mechanism (``objective reduction'') proposed to explain quantum state reduction is analyzed in light of the possible existence of large extra dimensions in the Arkani-Hamed, Dvali, Dimopoulos scenario. By calculating order-of-magnitude estimates for nucleon superpositions, it is shown that if the mechanism at question is correct, constraints may be placed on the number and size of extra dimensions. Hence, measurement of superposition collapse times (e.g. through diffraction or reflection experiments) could represent a new probe of extra dimensions. The influence of a time-dependent gravitational constant on the gravity-driven collapse scheme with and without the presence of extra dimensions also is discussed.

Publisher’s Note: Discrimination of supersymmetry and universal extra dimensions at hadron colliders [Phys. Rev. D72, 096006 (2005)

We contrast the experimental signatures of low energy supersymmetry and the model of Universal Extra Dimensions and discuss various methods for their discrimination at hadron colliders. We study the discovery reach of the Tevatron and the LHC for level 2 Kaluza-Klein modes, which would indicate the presence of extra dimensions. We find that with 100 ${\rm fb}^{-1}$ of data the LHC will be able to discover the $\gamma_2$ and $Z_2$ KK modes as separate resonances if their masses are below 2 TeV. We also investigate the possibility to differentiate the spins of the superpartners and KK modes by means of the asymmetry method of Barr.

Discrimination of supersymmetry and universal extra dimensions at hadron colliders

We contrast the experimental signatures of low energy supersymmetry and the model of Universal Extra Dimensions and discuss various methods for their discrimination at hadron colliders. We study the discovery reach of the Tevatron and the LHC for level 2 Kaluza-Klein modes, which would indicate the presence of extra dimensions. We find that with 100 fb −1 of data the LHC will be able to discover the γ2 and Z2 KK modes as separate resonances if their masses are below 2 TeV. We also investigate the possibility to differentiate the spins of the superpartners and KK modes by means of the asymmetry method of Barr.

Hawking radiation from a [formula omitted]-dimensional rotating black hole on the brane

We study the emission of Hawking radiation in the form of scalar fields from a (4+n)-dimensional, rotating black hole on the brane. We perform a numerical analysis to solve both the radial and angular parts of the scalar field equation, and derive exact results for the Hawking radiation energy emission rate. We find that, in 5 dimensions, as the angular momentum increases, the emission rate is suppressed in the low-energy regime but significantly enhanced in the intermediate and high-energy regimes. For higher values of n, the Hawking radiation emission rate on the brane is significantly enhanced, with the angular momentum, over the whole energy regime. We also investigate the energy amplification due to the effect of super-radiance and demonstrate that, in the presence of extra dimensions, this effect is again significantly enhanced.

Supersymmetry breaking with extra dimensions

This talk reviews some aspects of supersymmetry breaking in the presence of extra dimensions. The first part is a general introduction, recalling the motivations for supersymmetry and extra dimensions, as well as some unsolved problems of four-dimensional models of supersymmetry breaking. The central part is a more focused introduction to a mechanism for (super)symmetry breaking, proposed first by Scherk and Schwarz, where extra dimensions play a crucial role. The last part is devoted to the description of some recent results and of some open problems.

CMB anisotropies in the presence of extra dimensions

We discuss the effect of the time evolution of extra dimensions on CMB anisotropies and large-scale structure formation. We study the impact of scalar fields in a low-energy effective description of a general class of brane world models on the temperature anisotropy power spectrum. We show that when the coupling between these scalar fields and matter evolves over cosmological time scales, current observations of the CMB anisotropies can constrain primordial values of the fields in a manner complementary to local, late-time tests of gravity. We also present the effect of these fields on the polarization anisotropy spectra and the growth of large-scale structure, showing that future CMB observations will constrain theories of the Universe involving extra dimensions even further.

Bending of Light and Gravitational Signals in Certain On-Brane and Bulk Geometries

In this article, we first investigate the bending of light rays in 4D line elements representing spherically symmetric, static on–brane geometries. The amount of bending in these four dimensional, strong and weak field solutions is derived. Signatures, which appear in the bending formulae, due to the presence of extra dimensions are discussed. Subsequently, as a separate exercise, we calculate the bending of null geodesic trajectories in a bulk five dimensional spacetime with a Schwarzschild line element on the 3-brane section. We interpret the deviation of null trajectories as that of gravitational signals or five dimensional ‘photons,’ which are, unlike light rays confined to four dimensions, allowed to propagate along the fifth (extra) dimension. Features of the presence of extra dimensions in the effective potentials and the bending formula are analysed in this context.

Supernova constraint on bulk Majorons

In models with large extra dimensions all gauge singlet fields can in principle propagate in the extra dimensional space. We have investigated possible constraints on Majoron models of neutrino masses in which the Majorons propagate in extra dimensions. It is found that astrophysical constraints from supernovae are many orders of magnitude stronger than previous accelerator bounds. Our findings suggest that unnatural types of the ``seesaw'' mechanism for neutrino masses are unlikely to occur in nature, even in the presence of extra dimensions.

Adjoint bulk scalars and supersymmetric unification in the presence of extra dimensions

There are several advantages of introducing adjoint superfields at intermediate energies around $M=10^{13}$ GeV. Such as (i) gauge couplings still unify (ii) neutrino masses and mixings are produced (iii) primordial lepton asymmetry can be produced. We point out that if adjoint scalars have bulk excitations along with gauge bosons whereas fermions and the doublet scalar live on boundary then N=2 supersymmetric beta functions $\tilde{b_i}$ vanish. Thus even if extra dimensions open up at an intermediate scale $\mu_0$ and all N=2 Yang-Mills fields as well as N=2 matter fields in the adjoint representation propagate in the bulk, still gauge couplings renormalize beyond $\mu_0$ just like they do in 4-dimensions with adjoint scalars. Consequently unification is achieved in the presence to extra dimensions, mass scales are determined uniquely via Renormalization Group Equations(RGE) and unification scale remains high enough to suppress proton decay. This scenario can be falsified if we get signatures of extra dimensions at low energy.

The role of initial conditions in presence of extra dimensions

Quantum field theory in 4+1 dimensional bulk space with boundary, representing a 3-brane, is considered. We study the impact of the initial conditions in the bulk on the field dynamics on the brane. We demonstrate that these conditions determine the Kaluza-Klein measure. We also establish the existence of a rich family of quantum fields on the brane, generated by the same bulk action, but corresponding to different initial conditions. A simple classification of these fields is proposed and it is shown that some of them lead to ultraviolet finite theories, which have some common features with strings.

Effects of extra dimensions on unitarity and the Higgs boson mass

We study the unitarity constraint on two body Higgs boson elastic scattering in the presence of extra dimensions. The contributions from the exchange of spin-2 and spin-0 Kaluza-Klein states can have a large effect on the partial wave amplitude. The unitarity condition restricts the maximal allowed value for the ratio $r=\sqrt{s}{/M}_{S}$ of the center of mass energy $\sqrt{s}$ to the gravity scale ${M}_{S}$ to be less than one. Although the constraint on the standard Higgs boson mass for r of order one is considerably relaxed, for small r the constraint is similar to that in the standard model. The resulting bound on the Higgs boson mass is not dramatically altered if perturbative calculations are required to be valid up to the maximal allowed value for r.

The effective early universe in the presence of extra dimensions

The Robertson-Walker geometry in an empty five-dimensional universe is derived, and the effective four-dimensional evolution is analyzed. The radius of the compact fifth dimension is regarded as a non-static quantity. The “fine structure” constancy is asymptotically respected only provided the cosmological constant vanishes and the ordinary three-space is open. Characteristically, the evolution of the very early universe is governed by the Zeldovich equation of state P= ϱ.