{"arxiv_id":"hep-ph/0312002","title":"Disformal Inflation","abstract":"We show how short inflation naturally arises in a non-minimal gravity theory with a scalar field without any potential terms. This field drives inflation solely by its derivatives, which couple to the matter only through the combination $\\bar g_{\\mu\\nu} = g_{\\mu\\nu} - \\frac{1}{m^4} \\partial_\\mu \\phi \\partial_\\nu \\phi$. The theory is free of instabilities around the usual Minkowski vacuum. Inflation lasts as long as $\\dot \\phi^2 > m^4$, and terminates gracefully once the scalar field kinetic energy drops below $m^4$. The total number of e-folds is given by the initial inflaton energy $\\dot \\phi_0^2$ as ${\\cal N} \\simeq \\frac13 \\ln(\\frac{\\dot \\phi_0}{m^2})$. The field $\\phi$ can neither efficiently reheat the universe nor produce the primordial density fluctuations. However this could be remedied by invoking the curvaton mechanism. If inflation starts when $\\dot \\phi^2_0 \\sim M^4_P$, and $m \\sim m_{EW} \\sim TeV$, the number of e-folds is ${\\cal N} \\sim 25$. Because the scale of inflation is low, this is sufficient to solve the horizon problem if the reheating temperature is $T_{RH} \\ga MeV$. In this instance, the leading order coupling of $\\phi$ to matter via a dimension-8 operator $\\frac{1}{m^4}\\partial_\\mu \\phi \\partial_\\nu \\phi ~ T^{\\mu\\nu}$ would lead to fermion-antifermion annihilation channels $f\\bar f \\to \\phi \\phi$ accessible to the LHC, while yielding very weak corrections to the Newtonian potential and to supernova cooling rates, that are completely within experimental limits.","primary_cat":"hep-ph","cross_cats":["astro-ph","gr-qc","hep-th"],"submitted_at":"2003-11-29T20:21:18+00:00","latest_version":2,"source":"arxiv","source_label":"arXiv","source_url":null,"has_pdf":true,"has_source":false,"verdict":"CONDITIONAL","confidence":"HIGH","one_line_summary":"Coupling matter to a derivative-dependent metric lets a potential-free scalar field drive about 25 e-folds of low-scale inflation, ending when its kinetic energy drops below the disformal mass scale.","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","upvotes":0,"downvotes":0,"pith_score":0,"inbound_count":17,"_links":{"html":"https://pith.science/paper/hep-ph/0312002","verdict":"/api/v1/verdicts/hep-ph/0312002"}}