Narrow Results

We investigate the SU(3)³ GUT model when signs of the model (precursors), due to low compactification scale, appear before the gauge couplings of the Standard Model get unified. The Kaluza–Klein state contribution seems to lead the gauge couplings to unification through a wide energy scale only in the case when the colour group is augmented to SU(4).

A five-dimensional Einstein spacetime with (non)vanishing cosmological constant is analyzed in detail. The metric is in close analogy with the four-dimensional massless uncharged C-metric in many aspects. The coordinate system, horizons and causal structures, relations to standard form of de Sitter, anti de Sitter and Minkowski vacua are investigated. After a boost and Kaluza–Klein reduction, we get an exact solution of four-dimensional Einstein–Maxwell–Liouville theory which reduces to a solution to Einstein–Liouville theory in the limit of zero boost velocity and to that of Einstein–Maxwell–dilaton theory in the case of zero cosmological constant.

In the present study, we mainly investigate the nature of entropy function in non-flat Kaluza–Klein universe. We prove that the first and generalized second laws of gravitational thermodynamics are valid on the dynamical apparent horizon.

In this paper I introduce tensor multinomials, an algebra that is dense in the space of nonlinear smooth differential operators, and use a subalgebra to create an extension of Einstein’s theory of general relativity. In a mathematical sense this extension falls between Einstein’s original theory of general relativity in four dimensions and the Kaluza–Klein theory in five dimensions. The theory has elements in common with both the original Kaluza–Klein and Brans–Dicke, but emphasizes a new and different underlying mathematical structure. Despite there being only four physical dimensions, the use of tensor multinomials naturally leads to expanded operators that can incorporate other fields. The equivalent Ricci tensor of this geometry is robust and yields vacuum general relativity and electromagnetism, as well as a Klein–Gordon-like quantum scalar field. The formalism permits a time-dependent cosmological function, which is the source for the scalar field. I develop and discuss several candidate Lagrangians. Trial solutions of the most natural field equations include a singularity-free dark energy dust cosmology.

This work deals with the Kaluza–Klein cosmological model with strange-quark-matter in $f(R,T)$ theory of gravity, where R is the Ricci scalar and T is the trace of the energy–momentum tensor. To determine the solution of the field equation, we have assumed that scalar expansion $\theta$ is proportional to shear scalar ${\sigma }^2$ which leads to $R=A^m$, where R and A are metric potentials and m is constant. The cosmological parameters are investigated with the help of the equation of state strange-quark-matter (SQM) is $p=\frac{\rho -4B_c}{3}$, where $B_c$ is Bag constant. We have concentrated on the distances of cosmology such as the look-back time, proper distance, luminosity distance, angular-diameter distance and distance modulus which are presented graphically by using suitable data of $H_0$. The physical and geometrical properties of models are also discussed.

In this paper, we examine certain aspects of magnetized spacetime solutions within the Einstein–Maxwell–dilaton theory. Specifically, we discuss the Melvin-like universe and compare it to the equivalent solution in the Einstein–Maxwell case. Additionally, we analyze the equatorial circular motions and corresponding electromagnetic fields within this spacetime. Some distinguished properties compared to the magnetized black hole in Einstein–Maxwell case are found.

It is shown that the coupling of the Kaluza-Klein (KK) internal scalar field both to an external stabilizing bulk scalar field and to the geomagnetic field may explain the observed dispersion in laboratory measurements of the (effective) gravitational constant. Except the PTB 95 value, the predictions are found in good agreement with all of the experimental data. The cosmological variation of the fine-structure constant is also addressed.

The PAMELA satellite-borne experiment¹, to be launched in 2005, is a powerful spectrometer including a magnetic field tracker and particle identification detectors. PAMELA science is broad and includes studies of interstellar propagation, solar modulation and search for dark matter signals.

The perfect-fluid cosmology in the (1+d+D)-dimensional Kaluza–Klein space–times for an arbitrary barotropic equation of state p = (γ-1)ρ is quantized by using the Schutz's variational formalism. We make efforts in the mathematics to solve the problems in two cases. In the first case of the stiff fluid γ = 2 we exactly solve the Wheeler–DeWitt equation when the d space is flat. After the superposition of the solutions the wave-packet function is obtained exactly. We analyze the Bohmian trajectories of the final-stage wave-packet functions and show that the scale functions of the flat d spaces and the compact D spaces will eventually evolve into the nonzero finite values. In the second case of γ≈2, we use the approximated wave function in the Wheeler–DeWitt equation to find the analytic forms of the final-stage wave-packet functions. After analyzing the Bohmian trajectories we show that the flat d spaces will be expanding forever while the scale function of the contracting D spaces would not become zero within finite time. Our investigations indicate that the quantum effect in the quantum perfect-fluid cosmology could prevent the extra compact D spaces in the Kaluza–Klein theory from collapsing into a singularity or that the "crack-of-doom" singularity of the extra compact dimensions is made to occur at t = ∞.

A major focus at the Large Hadron Collider (LHC) will be on Higgs boson studies and it would be an interesting prospect to simultaneously probe for physics beyond the Standard Model in the Higgs signals. In this work we show as to what extent, the effects of universal extra dimension (UED) can be isolated at the LHC through the Higgs signals. By doing a detailed study of the different uncertainties involved in the measurement of the rates for the process pp →h →γγ, we estimate the extent to which these uncertainties can mask the effects of the contributions coming from UED.

We analyze some unphysical features of the geodesic approach to matter coupling in a compactified Kaluza-Klein scenario, like the q/m puzzle and the huge massive modes. We propose a new approach, based on Papapetrou multipole expansion, that provides a new equation for the motion of a test particle. We show how this equation provides right couplings and does not generate huge massive modes.

Novel static, time-dependent and spatial–temporal solutions to Einstein field equations, displaying singularities, with and without horizons, and in several dimensions, are found based on a dimensional reduction procedure widely used in Kaluza–Klein-type theories. The Kerr–Newman black hole entropy as well as the Reissner–Nordstrom, Kerr and Schwarzschild black hole entropy are derived from the corresponding Euclideanized actions. A very special cosmological model based on the dynamical interior geometry of a black hole is found that has no singularities at t = 0 due to the smoothing of the mass distribution. We conclude with another cosmological model equipped also with a dynamical horizon and which is related to Vaidya's metric (associated with the Hawking radiation of black holes) by interchanging t ↔ r, which might render our universe a dynamical black hole.

In the full type IIB open superstring setup, we show that there exists a vertex operator, denoted by V_L, whose renormalization reproduces the same anomalous dimension matrix that was obtained by Minahan and Zarembo (MZ) [J. High Energy Phys. 0303, 013 (2003)]. The vertex operator is a gauge singlet, and has the same SO(6) index structure as the operator used by MZ. To obtain the SYM anomalous dimensions, one of the key ingredients is the non-abelianization of the nonlinear sigma model action in a D-brane background. Park [Phys. Lett. B 660, 583 (2008)] conjectured that quantum effects of open strings on a stack of D-branes should generate the curvature. Even though the conjecture had passed a few consistency checks, the role of the higher order curvature terms has remain mostly unobserved until now. By choosing a special form of the non-abelianized counter vertex, V_G, we show that the SYM result is reproduced. We comment on fermionic completion of V_L and on how the special form of the non-Abelian vertex V_G may arise.

The observation of magnetic monopoles would lead to a symmetrization of Maxwell’s equations and provide explanations of fundamental properties such as the quantization of electric charge. Yet, in four dimensions, the covariant electromagnetic field tensor yields an action whose resulting field equations establish the absence of a magnetic charge. We here study the existence of magnetic monopoles in an extended space–time with a second time dimension, and construct the higher-dimensional gauge potential. This motivates the use of the Kalb–Ramond field, upon which a Kaluza–Klein-like reduction is performed under the assumption that the two time dimensions have no co-dependency. The resulting 5D electrodynamics contains a generalized version of Maxwell’s equations which contain magnetic charge densities whose source potential obeys a five-dimensional wave equation. As a second time dimension only acts on small length scales in the order of the Planck length, we provide a theory with symmetrized Maxwell’s equations including magnetic monopoles which do not violate current experimental evidence. We finally discuss the subsequent quantization of the electric charge as well as the weak interaction, equivalent to the violation of time reversal.

Experiments were performed in vacuum to examine a modified Kaluza–Klein theory. Originally proposed by Mbelek and Lachièze-Rey, the 5D Kaluza–Klein-$\psi$ theory includes an external scalar field $\psi$ to couple gravitational and electromagnetic fields and can be used to explain some misunderstood phenomena in physics. The theory predicts that a pendulum will experience detectable forces exceeding predictions from classical electromagnetism when interacting with a scalar field. In this experiment, a dielectric mirror is hung as a pendulum inside a vacuum chamber and its oscillations are examined with two laser interferometers. In proximity to the pendulum, different solenoids and toroids will induce magnetic fields that can also be shielded to a great extent using a Gauss chamber. The experiments were conducted in a vacuum chamber to allow the measurement of torsion angles as low as 0.1arcsec above the noise, as well as 0.1$\mu$m translations of the pendulum. The phenomenon observed differs from what was observed by Mbelek at ambient pressure in both magnitude and behavior. Dummy test results hint at the presence of convection effects to explain the pendulum’s rotation, which was eliminated under higher vacuum and by placing a wall between the solenoid and pendulum. In the presence of stronger magnetic fields, the pendulum’s translation was observed to agree with effects predicted by a consideration of diamagnetic effects.

We propose a mechanism for the origin of matter in the universe in the framework of Einstein–Gauss–Bonnet gravity in higher dimensions. The new static black hole solution recently discovered by the authors,¹ with the Kaluza–Klein split of space–time as a product of the usual with a space of negative constant curvature, is indeed a pure gravitational creation of a black hole which is also endowed with a Maxwell-like gravitational charge in four-dimensional vacuum space–time. This solution has been further generalized to include radially flowing radiation, which means that extra-dimensional curvature also produces matter distribution asymptotically, resembling charged null dust. The static black hole could thus be envisioned as being formed from anti–de Sitter space–time by the collapse of radially inflowing charged null dust. It thus establishes the remarkable reciprocity between matter and gravity — as matter produces gravity (curvature), gravity produces matter. After the Kaluza–Klein generation of the Maxwell field, this is the first instance of realization of matter without matter in the classical framework.

By considering the product of the usual four-dimensional space–time with two dimensional space of constant curvature, an interesting black hole solution has recently been found for Einstein–Gauss–Bonnet gravity. It turns out that this as well as all others could easily be made to radiate Vaidya null dust. However, there exists no Kerr analog in this setting. To get the physical feel of the four-dimensional black hole space–times, we study asymptotic behavior of stresses at the two ends, r → 0 and r → ∞.

In this paper, we have explored cold dark matter and holographic dark energy cosmological model with big rip singularity. To obtain the solution of the field equation, we supposed that scalar expansion $𝜃$ is proportional to shear scalar ${\sigma }^2$, which leads to $P_1={(P_2)}^n$, where $P_1$, $P_2$ are metric potentials and $n$ is constant. Big bang and big rip singularity are investigated. The state-finder parameter is analyzed. The physical and geometrical parameters of the universe are explained.

We present a Kaluza-Klein vacuum solution which closely resembles the Taub-NUT magnetic monopole and we investigate its physical properties as viewed from four space-time dimensions. We show that the Taub-NUT Kaluza-Klein vacuum solution in five dimensions is a static magnetic monopole. We find that the four dimensional matter properties do not obey the equation of state of radiation and there is no event horizon. A comparison with the available magnetic monopole solutions and the issue of vanishing and negative mass are discussed.

The Electroweak model will be geometrized in a 5-D Riemann-Cartan framework: U(1) weak hyper-charge group will be worked out in a Klauza-Klein scheme, while SU(2) weak isospin group will be identified to suitable bein projections of the contortion field. The possibility of introducing Ashtekar formalism in 5-D Klauza-Klein theories will be investigated.