[Paper Review] New developments on embedding inflation in gauge theory and particle physics

Anupam Mazumdar|ArXiv.org|Jul 23, 2007

Cosmology and Gravitation Theories84 references8 citations

TL;DR

This paper proposes that inflation in the Minimal Supersymmetric Standard Model (MSSM) can arise naturally from flat directions in the scalar potential, where the inflaton is a gauge-invariant combination of MSSM Higgs fields. The model achieves successful inflation via Hubble-induced corrections that stabilize a false vacuum, enabling a graceful exit that simultaneously produces the CMB perturbations, thermalized SM plasma, baryogenesis, and cold dark matter—offering a unified, testable framework within the MSSM gauge sector.

ABSTRACT

In this brief review we will discuss how a well motivated particle theory beyond the eletroweak Standard Model provides ingredients and conditions for a successful inflation. We will mainly focus on a low energy supersymmetric Standard Model which provides plenty of scalars. In particular, these scalars span a multidimensional moduli space of {\it gauge invariant} operators which carry the Standard Model charges. The inflationary predictions which matches the current observations are robust due to the fact that inflation occurs within our own gauge sector where the couplings are well known. We further argue that based on our current understandings if there exists a {\it string landscape} of multiple vacua, then it is very natural that the last phase of inflation would be driven by one of the many supersymmetric Standard Model modulii. Only such a graceful exit from inflation would provide hot thermal Standard Model baryons, cold dark matter, conditions for baryogenesis and foremost the seed density perturbations for the cosmic microwave background radiation in just {\it one package}. Furthermore we will also discuss how some of the ingredients of inflation can be tested already by the LHC.

Motivation & Objective

• To resolve the fundamental issue of inflaton origin by embedding inflation within the well-motivated MSSM gauge sector, avoiding ad hoc gauge singlet fields.
• To unify the reheating process post-inflation, ensuring thermalization of the Standard Model, baryogenesis, and cold dark matter production in a single mechanism.
• To provide a testable framework where inflation and its aftermath are tied to known particle physics, enabling LHC probes of inflationary dynamics.
• To address the limitations of string landscape models by showing that MSSM moduli can naturally drive inflation via Hubble-induced corrections.
• To demonstrate that successful inflation and a graceful exit are robust when the inflaton is a gauge-invariant MSSM scalar field with known couplings.

Proposed method

• Utilizes flat directions in the MSSM Higgs sector as candidates for the inflaton, which are gauge-invariant combinations of Standard Model scalars.
• Applies Hubble-induced corrections to the scalar potential, modifying the effective potential such that the inflaton field tracks a time-dependent false minimum.
• Derives conditions under which the effective mass and curvature of the potential (V''(φ_min)) remain larger than the Hubble rate, ensuring slow-roll inflation.
• Shows that as the false vacuum energy density decreases, the inflaton field evolves adiabatically to the true minimum, triggering a graceful exit.
• Demonstrates that reheating occurs via coherent oscillations of the MSSM flat direction, producing SM quanta and satisfying Big Bang Nucleosynthesis constraints.
• Uses the condition H_false > H_MSSM ~ 1 GeV to ensure the field reaches the required inflationary interval, relaxing prior constraints requiring H_false > 10^9 GeV.

Experimental results

Research questions

• RQ1 Can inflation be naturally embedded within the MSSM gauge sector without introducing ad hoc gauge singlet fields?
• RQ2 How can the inflaton's couplings and interactions be constrained by known particle physics symmetries and renormalizability?
• RQ3 What mechanism ensures a graceful exit from inflation that simultaneously produces thermal SM plasma, baryons, and cold dark matter?
• RQ4 How do Hubble-induced corrections stabilize the inflaton potential and enable slow-roll conditions in a dynamical vacuum?
• RQ5 Can the proposed inflationary mechanism be probed experimentally at the LHC through signatures of MSSM flat direction dynamics?

Key findings

• Inflation can be successfully realized within the MSSM gauge sector via flat directions of Higgs fields, which are gauge-invariant and carry Standard Model quantum numbers.
• The effective potential is modified by Hubble-induced corrections, leading to a time-dependent false minimum that the inflaton field tracks during inflation.
• The condition H_false > H_MSSM ~ 1 GeV ensures that the inflaton reaches the required field range for successful inflation, significantly relaxing prior constraints.
• The curvature of the potential at the false minimum, V''(φ_min) ~ 2(n-2)√|c| H_false m_φ, remains larger than the Hubble rate during inflation, ensuring slow-roll dynamics.
• When H_false drops below ~H_MSSM / (2(n-2)m_φ), the inflaton field begins to roll toward the true minimum, triggering reheating and production of SM particles.
• The reheating process naturally produces a thermal bath of SM degrees of freedom, satisfying Big Bang Nucleosynthesis constraints and enabling baryogenesis and cold dark matter production in one unified framework.