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Experimental Methods to Study Human Postural Control

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Backreaction during inflation: a physical gauge invariant formulation.

F Finelli¹, G Marozzi, G P Vacca

¹INAF/IASF Bologna, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna via Gobetti 101, I-40129 Bologna, Italy.

Physical Review Letters

|April 27, 2011

Summary

We investigate quantum backreaction from scalar fluctuations during cosmic inflation. Free-falling observers experience no backreaction under specific conditions, impacting effective Hubble rate and fluid equation of state.

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Area of Science:

Cosmology
Quantum Field Theory
General Relativity

Background:

Cosmological backreaction is crucial for understanding the universe's evolution.
Previous studies often lacked gauge invariance, limiting their applicability.
Scalar fluctuations during inflation are a key area of research.

Purpose of the Study:

To compute cosmological backreaction in a genuinely gauge-invariant manner.
To analyze the impact of scalar fluctuations on spacetime dynamics during inflation.
To identify conditions under which observers experience no scalar-induced backreaction.

Main Methods:

Development of a novel, genuinely gauge-invariant approach.
Utilizing effective equations to describe averaged geometry dynamics.
Analysis within a cosmological inflationary context.

Main Results:

A gauge-independent computation of quantum backreaction is achieved.
The impact of long-wavelength scalar fluctuations on spacetime is quantified.
Conditions are derived where free-falling (geodetic) observers show no scalar-induced backreaction.

Conclusions:

The developed gauge-invariant method provides a robust framework for cosmological backreaction studies.
Understanding observer-dependent backreaction is essential for accurate cosmological models.
Specific conditions can render scalar-induced backreaction negligible for certain observers.