Parity violating gravitational waves at the end of inflation

Abstract

Inflaton-vector interactions of the type ϕFF̃ have provided interesting phenomenology to tackle some of current problems in cosmology, namely the vectors could constitute the dark matter component. It could also lead to possible signatures imprinted in a gravitational wave spectrum. Through this coupling, a rolling inflaton induces an exponential production of the transverse polarizations of the vector field, having a maximum at the end of inflation when the inflaton field velocity is at its maximum. These gauge particles, already parity asymmetric, will source the tensor components of the metric perturbations, leading to the production of parity violating gravitational waves. In this work we examine the vector particle production in the weak coupling regime, integrating the gauge mode amplitudes spectrum during the entirety of its production and amplification epochs, until the onset of radiation domination. Finally, we calculate the gravitational wave spectrum combining the vector mode analytical solution, the WKB expansion, valid only during the amplification until horizon crossing, and the numerical solution obtained at the beginning of radiation domination when the modes cease to grow.

Directional detection of meV dark photons with Dandelion

“…On the other hand, transverse DP modes will source the tensor components of tensor perturbations after inflation ends. And given that tachyonic production of transverse DP only efficiently excites one of the transverse components of the DP, they lead to the production of parity violating gravitational waves (GW) [46][47][48][49]. Whether or not this GW spectrum can be detected by present and near future experiments is still an open question.…”

Present and future of C osmo

“…ALPs can very strongly excite gauge-field quanta through such Chern-Simons coupling. For example, in axion inflation scenarios, where the ALP is identified with the inflaton, the gauge field can be highly excited during inflation, leading to a rich phenomenology that includes: the production of a sizable background of chiral gravitational waves [212][213][214][215][216][217], which can be searched for with direct detection gravitational wave experiments [218][219][220][221]; the creation of large scalar perturbations [197,213,218,[222][223][224][225], which can be probed by the CMB [212,222,226] and searches for primordial black holes (PBHs) [197,[227][228][229][230][231][232][233][234]; efficient magnetogenesis [139,[235][236][237], baryon asymmetry [238][239][240][241][242][243] and reheating [198,244] mechanisms, which can also be naturally realized in these scenarios. Furthermore, due to interaction, equation ( 50), a dark matter ALP can als...…”

On the importance of heavy fields in pseudo-scalar inflation

“…The interesting phenomenology of this effect is quite rich. The large production of one of the gauge field helicities leads to the large equilateral primordial non-Gaussianity [19,20], chiral gravitational wave [21,[26][27][28][29][30], productions of primordial black holes [31][32][33][34] and large scale magnetic fields [17,18,24,[35][36][37]. The constrain of non-Gaussianity from CMB limit gives a upper bound of the parameter ξ ≲ 2.5 [15,38].…”