Physics

We consider that the cosmological constant is associated with the vacuum energy density of a particle physics model. In the path integral formalism of euclidean quantum gravity and in the background of the Robertson Walker metric we calculate only the contribution of the matter density to the fluctuating metric. This produces an effective term in the action that acts as a correction to the vacuum energy density of the matter. The method leads to the observed cosmological constant without the need of any fine tuning in the gravity or particle physics sectors.

The necessity of renormalization arises from the infinite integrals which are caused by the discrepancy between the orders of differential and integral operators in the four dimensional QFTs. Therefore in view of the fact that finiteness and invariant properties of operators are their topological aspects, essential renormalization tools to extract finite invariant values from those infinities which are comparable with the experimental results, e. g. regularization, perturbation and radiative corrections follow some topological standards. In the second part we consider dimensional and geometrical consequences of topological approach to renormalization for the geometrical structure and degrees of freedom of renormalized theory. We show that regularization and renormalization of QED are performed only by certain restrictive dimensional conditions on QED fields. Further it is shown that in accord with our previous topological approach to renormalization of QED the geometrical evaluation of applied dimensional renormalization conditions and the appearance of anomalies refer to a reduction of number of degrees of freedom according to the reduced symmetry of QED. A conclusion concerning a comparison of our results with holographic principle models is also included.

We demonstrate a direct correspondence between the basis states of the minimal ideals of the complex Clifford algebras Cℓ(6) and Cℓ(4) , shown earlier to transform as a single generation of leptons and quarks under the Standard Model's unbroken SU(3 ) c ×U(1 ) em and SU(2 ) L gauge symmetries respectively, and a simple topologically-based toy model in which leptons, quarks, and gauge bosons are represented as elements of the braid group B 3 . It was previously shown that mapping the basis states of the minimal left ideals of Cℓ(6) to specific braids replicates precisely the simple topological structure describing electrocolor symmetries in an existing topological preon model. This paper extends these results to incorporate the chiral weak symmetry by including a Cℓ(4) algebra, and identifying the basis states of the minimal right ideals with simple braids. The braids corresponding to the charged vector bosons are determined, and it is demonstrated that weak interactions can be described via the composition of braids.

This paper reports an experiment about abnormal deflection of cathode-ray in a specially designed odd-symmetric magnetic field. The measurement results show that during cathode ray passes through an odd-symmetric magnetic field, a deflection opposite to Lorentz force occurs at the boundary of magnetic fields. It can be explained by the inertial effect of the electron rotating on its axis in magnetic field, and Lorentz force is similar to the Magnus effect in fluid mechanics. In this paper, a mechanical model is used to analyze and calculate this explanation in detail, and the Maxwell's equations of electromagnetic field are derived.

Teleparallel gravity is a modified theory of gravity for which the Ricci scalar R of the underlying geometry in the action is replaced by an arbitrary functional form of torsion scalar T . In doing so, cosmology in gravity becomes greatly simplified owing to the fact that T contains only the first derivatives of the vierbeins. The article exploits this appealing nature of f(T) gravity and present cosmological scenarios from hybrid and logarithmic teleparallel gravity models of the form and f=Dlog(bT) respectively, where m , n , D and b are free parameters constrained to suffice the late time acceleration. We employ a well motivated parametrization of the deceleration parameter having just one degree of freedom constrained with a χ 2 test from 57 data points of Hubble data set in the redshift range 0.07<z<2.36 , to obtain the expressions of pressure, density and EoS parameter for both the teleparallel gravity models and study their temporal evolution. We find the deceleration parameter to experience a signature flipping for the χ 2 value of the free parameter at z tr ≃0.6 which is consistent with latest Planck measurements. Next, we present few geometric diagnostics of this parametrization to understand the nature of dark energy and its deviation from the Λ CDM cosmology. Finally, we study the energy conditions to check the consistency of the parameter spaces for both the teleparallel gravity models. We find the SEC to violate for both the models which is an essential recipe to obtain an accelerating universe.

In this paper, we have investigated some features of anisotropic accelerating Bianchi type-I cosmological model in the presence of two non-interacting fluids, i.e. one usual string and other dark energy fluid towards the gravitational field equations for the linear form of f(T) gravity, where \textit{T }be the torsion. To achieve a physically realistic solution of the field equations, we have considered an exact matter dominated volumetric power law expansion. The aspects of derived model are discussed with the help of solution and make the model at late times turn out to be flat Universe. Also, observed that the model has initially non-singular and stable while for whole expansion it is unstable. At an initial expansion 0.01≤t≤0.05 when the Universe start to expand to infinite expansion t>1.73 (break away from for small interval of cosmic time 0.06≤t≤1.73 ), there is a matter dominated era while for 0.06≤t≤1.73 it approaches the quintessence region. Also, the string exists in the early universe which is in agreement with constraints of CMBR data but with the expansion the string phase of the Universe disappears, i.e. we have an anisotropic fluid of particles.

The f(R,T) theory of gravitation is an extended theory of gravitation in which the gravitational action contains both the Ricci scalar R and the trace of energy momentum tensor T and hence the cosmological models based on f(R,T) gravity are eligible to describing late time acceleration of present universe. In this paper, we investigate an accelerating model of flat universe with linearly varying deceleration parameter (LVDP). We apply the linearly time varying law for deceleration parameters that generates a model of transitioning universe from early decelerating phase to current accelerating phase. We carry out the state-finder and Om(z) analysis, and obtain that LVDP model have consistency with astrophysical observations. We also discuss profoundly the violation of energy-momentum conservation law in f(R,T) gravity and dynamical behavior of the model.

The analogy between acoustics and classical electromagnetism has been studied and exploited by many authors, bringing a large benefit to theoretical acoustics. The aim of this work is not to repeat or summarize those findings here, which can be found elsewhere in the acoustic literature, but to point to the analogy with more modern covariant (and quantum) theory of electromagnetism. Newer and far less exploited analogy with the theory of relativity is also considered. The emphasize is again not on the well established theory, but on the novel concepts related to the nature of sound waves and mechanisms of their generation in the so-called acoustic spacetime. This should complement the existing theory of wave propagation in a curved acoustic spacetime. Lastly, in an attempt to formulate a unified acoustic theory including the analogue micro-scale phenomena, certain concepts of quantum field theory as well as the principle of least action are applied for acoustics in fluids. The result is classical acoustics in fluids expressed using the formalism of modern field theories.

In this document, we briefly introduce the effective field theories. We propose some novel ideas in this manuscript. We introduce a novel formalism of the effective field theories and we apply it to the effective field theories of large scale structures. The new formalism is based on functionals of the actions composing those theories. We discuss our findings in a Cosmological Gravitology framework. We present with a cosmological inference approach these results and we give a guideline of how we can disentangle the best candidate between those models with some latest understanding of model selection.

We argue, in the context of AdS/CFT correspondence, that the structure of the geometry dual to two entangled CFTs is a time non-orientable spacetime. Further, we elevate this argument to whatever entangled quantum systems. Accordingly, we should expect that entangled quantum systems (particles in subsidiary) to not experience the flow of time. As a result, the lifetime of entangled particles should be considerably longer than that of their unentangled counterparts.