Bridge Load Rating

The inspection and evaluation of bridges in Indiana is critical to ensure their safety to better serve the citizens of the state. Part of this evaluation includes bridge load rating. Bridge load rating, which is a measure of the safe load capacity of the bridge, is a logical process that is typically conducted by utilizing critical information that is available on the bridge plans. For existing, poorly-documented bridges, however, the load rating process becomes challenging to adequately complete because of the missing bridge information. Currently, the Indiana Department of Transportation (INDOT) does not have a prescribed methodology for such bridges. In an effort to improve Indiana load rating practices INDOT commissioned this study to develop a general procedure for load rating bridges without plans. The general procedure was developed and it was concluded that it requires four critical parts. These parts are bridge characterization, bridge database, field survey and inspection, and bridge load rating. The proposed procedure was then evaluated on two bridges in Indiana that do not have plans as a proof of concept. As a result, it was concluded that load rating of bridges without plans can be successfully completed using the general procedure. A flowchart describing the general procedure was created to make the load rating process more user-friendly. Additional flowcharts that summarize the general procedure for different type of bridges were also provided

Near Scale Invariance with Modified Dispersion Relations

We describe a novel mechanism to seed a nearly scale invariant spectrum of adiabatic perturbations during a non-inflationary stage. It relies on a modified dispersion relation that contains higher powers of the spatial momentum of matter perturbations. We implement this idea in the context of a massless scalar field in an otherwise perfectly homogeneous universe. The couplings of the field to background scalars and tensors give rise to the required modification of its dispersion relation, and the couplings of the scalar to matter result in an adiabatic primordial spectrum. This work is meant to explicitly illustrate that it is possible to seed nearly scale invariant primordial spectra without inflation, within a conventional expansion history.Comment: 7 pages and no figures. Uses RevTeX

Can We See Lorentz-Violating Vector Fields in the CMB?

We investigate the perturbation theory of a fixed-norm, timelike Lorentz-violating vector field. After consistently quantizing the vector field to put constraints on its parameters, we compute the primordial spectra of perturbations generated by inflation in the presence of this vector field. We find that its perturbations are sourced by the perturbations of the inflaton; without the inflaton perturbation the vector field perturbations decay away leaving no primordial spectra of perturbations. Since the inflaton perturbation does not have a spin-1 component, the vector field generically does not generate any spin-1 ``vector-type'' perturbations. Nevertheless, it will modify the amplitude of both the spin-0 ``scalar-type'' and spin-2 ``tensor-type'' perturbation spectra, leading to violations of the inflationary consistency relationship.Comment: 36 pages, 1 fig, RevTex4, Submitted to PR

Creating Statistically Anisotropic and Inhomogeneous Perturbations

In almost all structure formation models, primordial perturbations are created within a homogeneous and isotropic universe, like the one we observe. Because their ensemble averages inherit the symmetries of the spacetime in which they are seeded, cosmological perturbations then happen to be statistically isotropic and homogeneous. Certain anomalies in the cosmic microwave background on the other hand suggest that perturbations do not satisfy these statistical properties, thereby challenging perhaps our understanding of structure formation. In this article we relax this tension. We show that if the universe contains an appropriate triad of scalar fields with spatially constant but non-zero gradients, it is possible to generate statistically anisotropic and inhomogeneous primordial perturbations, even though the energy momentum tensor of the triad itself is invariant under translations and rotations.Comment: 20 pages, 1 figure. Uses RevTeX

Einstein-Cartan gravity with scalar-fermion interactions

In this paper, we have considered the g-essence and its particular cases, k-essence and f-essence, within the framework of the Einstein-Cartan theory. We have shown that a single fermionic field can give rise to the accelerated expansion within the Einstein-Cartan theory. The exact analytical solution of the Einstein-Cartan-Dirac equations is found. This solution describes the accelerated expansion of the Universe with the equation of state parameter $w=-1$ as in the case of $\Lambda$CDM model.Comment: 6 pages, title is change

Where does Cosmological Perturbation Theory Break Down?

We apply the effective field theory approach to the coupled metric-inflaton system, in order to investigate the impact of higher dimension operators on the spectrum of scalar and tensor perturbations in the short-wavelength regime. In both cases, effective corrections at tree-level become important when the Hubble parameter is of the order of the Planck mass, or when the physical wave number of a cosmological perturbation mode approaches the square of the Planck mass divided by the Hubble constant. Thus, the cut-off length below which conventional cosmological perturbation theory does not apply is likely to be much smaller than the Planck length. This has implications for the observability of "trans-Planckian" effects in the spectrum of primordial perturbations.Comment: 25 pages, uses FeynM

DSR as an explanation of cosmological structure

Deformed special relativity (DSR) is one of the possible realizations of a varying speed of light (VSL). It deforms the usual quadratic dispersion relations so that the speed of light becomes energy dependent, with preferred frames avoided by postulating a non-linear representation of the Lorentz group. The theory may be used to induce a varying speed of sound capable of generating (near) scale-invariant density fluctuations, as discussed in a recent Letter. We identify the non-linear representation of the Lorentz group that leads to scale-invariance, finding a universal result. We also examine the higher order field theory that could be set up to represent it

On A Cosmological Invariant as an Observational Probe in the Early Universe

k-essence scalar field models are usually taken to have lagrangians of the form ${\mathcal L}=-V(\phi)F(X)$ with $F$ some general function of $X=\nabla_{\mu}\phi\nabla^{\mu}\phi$. Under certain conditions this lagrangian in the context of the early universe can take the form of that of an oscillator with time dependent frequency. The Ermakov invariant for a time dependent oscillator in a cosmological scenario then leads to an invariant quadratic form involving the Hubble parameter and the logarithm of the scale factor. In principle, this invariant can lead to further observational probes for the early universe. Moreover, if such an invariant can be observationally verified then the presence of dark energy will also be indirectly confirmed.Comment: 4 pages, Revte

Supersymmetric extensions of k-field models

We investigate the supersymmetric extension of k-field models, in which the scalar field is described by generalized dynamics. We illustrate some results with models that support static solutions with the standard kink or the compact profile.Comment: 11 page