False vacuum energy dominated inflation with large rr and the importance of κs\kappa_s

We investigate to which extent and under which circumstances false vacuum energy ($V_0$) dominated slow-roll inflation is compatible with a large tensor-to-scalar ratio $r = O(0.1)$, as indicated by the recent BICEP2 measurement. With $V_0$ we refer to a constant contribution to the inflaton potential, present before a phase transition takes place and absent in the true vacuum of the theory, like e.g. in hybrid inflation. Based on model-independent considerations, we derive an upper bound on the possible amount of $V_0$ domination and highlight the importance of higher-order runnings of the scalar spectral index (beyond $\alpha_s$) in order to realise scenarios of $V_0$ dominated inflation. We study the conditions for $V_0$ domination explicitly with an inflaton potential reconstruction around the inflaton field value 50 e-folds before the end of inflation, taking into account the present observational data. To this end, we provide the up-to-date parameter constraints within $\Lambda$CDM + $r$ + $\alpha_s$ + $\kappa_s$ using the cosmological parameter estimation code Monte Python together with the Boltzmann code CLASS.Comment: 16 pages, 5 figures; v2: matches publication in JCA

Accurate determination of inflationary perturbations

We use a numerical code for accurate computation of the amplitude of linear density perturbations and gravitational waves generated by single-field inflation models to study the accuracy of existing analytic results based on the slow-roll approximation. We use our code to calculate the coefficient of an expansion about the exact analytic result for power-law inflation; this generates a fitting function which can be applied to all inflationary models to obtain extremely accurate results. In the appropriate limit our results confirm the Stewart--Lyth analytic second-order calculation, and we find that their results are very accurate for inflationary models favoured by current observational constraints.Comment: 9 pages LaTeX file with 3 figures incorporated, using RevTeX and eps

A numerical simulation of pre-big bang cosmology

We analyse numerically the onset of pre-big bang inflation in an inhomogeneous, spherically symmetric Universe. Adding a small dilatonic perturbation to a trivial (Milne) background, we find that suitable regions of space undergo dilaton-driven inflation and quickly become spatially flat ($\Omega \to 1$). Numerical calculations are pushed close enough to the big bang singularity to allow cross checks against previously proposed analytic asymptotic solutions.Comment: 19 pages, revtex, matlab code available at http://www.fis.unipr.it/~onofr

Inflation and the User Cost of Capital: Does Inflation Still Matter?

In the late 1970s, many economists argued that the deleterious effects of inflation on the user cost of capital for U.S. firms were large. Since that time, the tax code has changed, the level of inflation has dropped significantly, and the of investment has evolved considerably. In this paper, we demonstrate that the net effect of these changes has--under reasonable assumptions--not relegated inflation to the sidelines. Indeed, we conclude that: (1) inflation, even at its relatively low current rates, continues to increase the user cost of capital significantly; (2) the marginal gain in investment in response to a percentage-point reduction in inflation is larger for lower levels of inflation; (3) the beneficial effects for steady-state consumption of lowering inflation even further than has been achieved to date would likely be significant; and (4) inflation has only a small impact on intratemporal distortion in the allocation of capital within the domestic business sector. We also show that the magnitude of the inflation effect on the user cost of capital is likely much smaller in open economies.

DEFROST: A New Code for Simulating Preheating after Inflation

At the end of inflation, dynamical instability can rapidly deposit the energy of homogeneous cold inflaton into excitations of other fields. This process, known as preheating, is rather violent, inhomogeneous and non-linear, and has to be studied numerically. This paper presents a new code for simulating scalar field dynamics in expanding universe written for that purpose. Compared to available alternatives, it significantly improves both the speed and the accuracy of calculations, and is fully instrumented for 3D visualization. We reproduce previously published results on preheating in simple chaotic inflation models, and further investigate non-linear dynamics of the inflaton decay. Surprisingly, we find that the fields do not want to thermalize quite the way one would think. Instead of directly reaching equilibrium, the evolution appears to be stuck in a rather simple but quite inhomogeneous state. In particular, one-point distribution function of total energy density appears to be universal among various two-field preheating models, and is exceedingly well described by a lognormal distribution. It is tempting to attribute this state to scalar field turbulence.Comment: RevTeX 4.0; 16 pages, 9 figure

Features and risks of Treasury Inflation Protection Securities

In 1997, the U.S. Treasury began the quarterly issuance of inflation indexed bonds, called Treasury Inflation Protection Securities (TIPS). So far, the Treasury has issued both 5-year and 10-year indexed bonds and will begin to issue 30-year indexed bonds and inflation indexed savings bonds in 1998. TIPS differ from conventional Treasury bonds in both their payment flows and risks. With virtually no inflation risk, they are the safest assets currently available in the U.S. market. Combined with conventional Treasury bonds, they allow investors to separate inflation risk from real interest rate risk and thus manage risk more efficiently.> To help investors understand and take full advantage of these new securities, Shen discusses the features and risks of the Treasury inflation indexed bonds. She explains why these bonds can benefit many investors and shows how the tax code prevents these bonds from being entirely inflation-risk free. Finally, she shows that historically the market risk of an indexed bond has been small compared to that of a conventional bond with similar maturity.Government securities ; Indexation (Economics)

Inflation and the personal tax code: assessing indexation

A reexamination of the potential costs of anticipated inflation in view of the inflation indexing system established during the 1980s.Income tax ; Inflation (Finance)

Bayesian Analysis of Inflation: Parameter Estimation for Single Field Models

Future astrophysical datasets promise to strengthen constraints on models of inflation, and extracting these constraints requires methods and tools commensurate with the quality of the data. In this paper we describe ModeCode, a new, publicly available code that computes the primordial scalar and tensor power spectra for single field inflationary models. ModeCode solves the inflationary mode equations numerically, avoiding the slow roll approximation. It is interfaced with CAMB and CosmoMC to compute cosmic microwave background angular power spectra and perform likelihood analysis and parameter estimation. ModeCode is easily extendable to additional models of inflation, and future updates will include Bayesian model comparison. Errors from ModeCode contribute negligibly to the error budget for analyses of data from Planck or other next generation experiments. We constrain representative single field models (phi^n with n=2/3, 1, 2, and 4, natural inflation, and "hilltop" inflation) using current data, and provide forecasts for Planck. From current data, we obtain weak but nontrivial limits on the post-inflationary physics, which is a significant source of uncertainty in the predictions of inflationary models, while we find that Planck will dramatically improve these constraints. In particular, Planck will link the inflationary dynamics with the post-inflationary growth of the horizon, and thus begin to probe the "primordial dark ages" between TeV and GUT scale energies.Comment: 16 pages, 9 figures. Updated to match published version (revised and expanded discussions of reheating uncertainties and slow roll mapping; references added; results unchanged). Code available at http://zuserver2.star.ucl.ac.uk/~hiranya/ModeCode