We study a two-parameter family of exactly solvable inflation models with variable sound speed, and derive a corresponding exact expression for the spectrum of curvature perturbations. We generalize this expression to the slow roll case, and derive an approximate expression for the scalar spectral index valid to second order in slow roll. We apply the result to the case of DBI inflation, and show that for certain choices of slow roll parameters, the Bunch-Davies limit (a) does not exist, or (b) is sensitive to stringy physics in the bulk, which in principle can have observable signatures in the primordial power spectrum.PACS numbers: 98.80.Cq

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We consider non-canonical generalizations of two classes of single-field inflation models. First, we study the non-canonical version of "ultra-slow roll" inflation, which is a class of inflation models for which quantum modes do not freeze at horizon crossing, but instead evolve rapidly on superhorizon scales. Second, we consider the non-canonical generalization of the simplest "chaotic" inflation scenario, with a potential dominated by a quadratic (mass) term for the inflaton. We find a class of related non-canonical solutions with polynomial potentials, but with varying speed of sound. These solutions are characterized by a constant field velocity, and we dub such models isokinetic inflation. As in the canonical limit, isokinetic inflation has a slightly red-tilted power spectrum, consistent with current data. Unlike the canonical case, however, these models can have an arbitrarily small tensor/scalar ratio. Of particular interest is that isokinetic inflation is marked by a correlation between the tensor/scalar ratio and the amplitude of non-Gaussianity such that parameter regimes with small tensor/scalar ratio have large associated non-Gaussianity, which is a distinct observational signature.

We study DBI inflation based upon a general model characterized by a power-law flow parameter ǫ(φ) ∝ φ α and speed of sound cs(φ) ∝ φ β , where α and β are constants. We show that in the slow-roll limit this general model gives rise to distinct inflationary classes according to the relation between α and β and to the time evolution of the inflaton field, each one corresponding to a specific potential; in particular, we find that the well-known canonical polynomial (large-and small-field), hybrid and exponential potentials also arise in this non-canonical model. We find that these noncanonical classes have the same physical features as their canonical analogs, except for the fact that the inflaton field evolves with varying speed of sound; also, we show that a broad class of canonical and D-brane inflation models are particular cases of this general non-canonical model. Next, we compare the predictions of large-field polynomial models with the current observational data, showing that models with low speed of sound have red-tilted scalar spectrum with low tensorto-scalar ratio, in good agreement with the observed values. These models also show a correlation between large non-gaussianity with low tensor amplitudes, which is a distinct signature of DBI inflation with large-field polynomial potentials.PACS numbers: 98.80.Cq

We present projections for reconstruction of the inflationary potential expected from ESA's upcoming Planck Surveyor CMB mission. We focus on the effects that tensor perturbations and the presence of non-Gaussianities have on reconstruction efforts in the context of non-canonical inflation models. We consider potential constraints for different combinations of detection/null-detection of tensors and non-Gaussianities. We perform Markov Chain Monte Carlo and flow analyses on a simulated Planck-precision data set to obtain constraints. We find that a failure to detect nonGaussianities precludes a successful inversion of the primordial power spectrum, greatly affecting uncertainties, even in the presence of a tensor detection. In the absence of a tensor detection, while unable to determine the energy scale of inflation, an observable level of non-Gaussianities provides correlations between the errors of the potential parameters, suggesting that constraints might be improved for suitable combinations of parameters. Constraints are optimized for a positive detection of both tensors and non-Gaussianities.

Posterior thrombus deposition in AAAs is associated with significantly lower growth rate and lower posterior maximum wall stress compared with that of AAAs with anterior thrombus deposition and could potentially indicate a lower rupture risk.

A mathematical model for the description of biomagnetic fluid flow exposed to a magnetic field that accounts for both electric and magnetic properties of the biofluid is presented. This is achieved by adding the Lorentz and magnetization forces in the Navier-Stokes equations. To demonstrate the effects of magnetic fields, we consider the case of laminar, incompressible, viscous, the steady flow of a Newtonian biomagnetic fluid (i) between two parallel plates; and (ii) through a straight rigid tube with a 60% in diameter, 84% on area, axisymmetric stenosis. Two external magnetic fields were investigated: one produced by an infinite wire carrying constant current, and a dipole-like field. We show, numerically and analytically, that the wire produces an irrotational force that, independent of its intensity, only alters the pressure leaving the velocity field unaffected. In contrast, when the fluid is exposed to the dipole-like field, which generates a rotational force, then both pressure and velocity can be strongly influenced even at moderate field strengths. Similar trends were obtained when a time varying flow is simulated through the axisymmetric stenosis in the presence of the dipole-like rotational magnetic field. It is expected that our findings could have important applications in blood flow control.

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