Perturbative QFT calculations in de Sitter space are riddled with contributions that diverge over time. These contributions often arise from loop integrals, which are notoriously hard to compute in de Sitter. We discuss an approach to evaluate such loop integrals, for a scalar field theory in a fixed de Sitter background. Our method is based on the Mellin-Barnes representation of correlation functions, which allow us to regulate divergences for scalars of any mass while preserving the de Sitter symmetries. The resulting expressions have a similar structure as a standard answer from dimensional regularization in flat space QFT. These features of the regulator are illustrated with two examples, worked out in detail. Along the way, we illuminate the physical origin of these divergences and their interpretation with the machinery of the dynamical renormalization group. Our approach regulates the IR divergences of massless and massive particles in the same way. For massless scalars, the loop corrections can be incorporated as systematic improvements to the Stochastic Inflation framework, allowing for a more precise description of the IR dynamics of such fields in de Sitter.

Non-trivial inflaton self-interactions can yield calculable signatures of primordial non-Gaussianity that are measurable in cosmic surveys. Surprisingly, we find that the phase transition to slow-roll eternal inflation is often incalculable in the same models. Instead, this transition is sensitive to the non-Gaussian tail of the distribution of scalar fluctuations, which probes physics inside the horizon, potentially beyond the cutoff scale of the Effective Field Theory of Inflation. We demonstrate this fact directly by calculating non-Gaussian corrections to Stochastic Inflation within the framework of Soft de Sitter Effective Theory, from which we derive the associated probability distribution for the scalar fluctuations. We find parameter space consistent with current observations and weak coupling at horizon crossing in which the large fluctuations relevant for eternal inflation can only be determined by appealing to a UV completion. We also show this breakdown of the perturbative description is required for the de Sitter entropy to reflect the number of de Sitter microstates.

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Ceramic, polymers and solid lubricants were used as reinforcements in the electroless Ni-P deposit, which is in-soluble in nature. Impingement of in-soluble particles has improved the hardness and wear resistance of the Ni-P deposit. However, the question still remains on the bonding of matrix and reinforcement particle during the wear at high load conditions. Hence, to strengthen the Ni-P deposit, a soluble reinforcement particle (CaBr 2 ) has been used in this study. A detail study on the role of bath composition (Nickel sulphate and CaBr 2 ) on the mechanical and tribology behavior of alkaline electroless Ni-P/CaBr 2 composite coatings is reported. Coatings were carried out with various weight combination of CaBr 2 particle (1 g l −1 , 2 g l −1 , and 3 g l −1 ) and source of nickel (16 g l −1 , 18 g l −1 , and 20 g l −1 ) in the bath. The optimum bath composition to achieve higher hardness, low surface roughness (Ra), low coefficient of friction (COF), and wear rate were analyzed using response surface methodology (RSM). ANOVA was used to identify the influencing factor on the output responses and an empirical model has been formulated. Ni-P/CaBr 2 coating exhibited a high surface roughness of 1.505 μm for the weight combination of 1 g l −1 of CaBr 2 and 20 g l −1 of nickel sulphate. High surface hardness of 793 HV 0.05 and low wear rate of 3.33×10 −6 gm.m −1 was achieved for the high weight combination of CaBr 2 particle and nickel sulphate. The obtained experimental results were closer to the predicted results, confirming the significance of the model for optimizing the bath composition for Ni-P/CaBr 2 composite coatings. Various characterization techniques like Scanning Electron Microscope-Electron Dispersive Spectrum (SEM-EDS), x-ray Diffractometer (XRD) and 3D noncontact surface profilometer were used to justify the wear results obtained through the experimentation.

Non-trivial inflaton self-interactions can yield calculable signatures of primordial non-Gaussianity that are measurable in cosmic surveys. We calculate the non-Gaussian corrections to Stochastic Inflation within the framework of Soft de Sitter Effective Theory, from which we derive the associated probability distribution for the scalar fluctuations. As a consequence of this new result, we show that the phase transition to slow-roll eternal inflation is often incalculable in these models. Instead, this transition is sensitive to the non-Gaussian tail of the distribution of scalar fluctuations, which probes physics inside the horizon, potentially beyond the cutoff scale of the Effective Field Theory of Inflation. We delineate the parameter space consistent with current observations and weak coupling at horizon crossing in which the large fluctuations relevant for eternal inflation can only be determined by appealing to a UV completion. We also argue that this breakdown of the perturbative description is required for the de Sitter entropy to reflect the number of de Sitter microstates.

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