text: 133,75,1253205923511877638,1177063549606203394,Tommi Tenkanen,"A new paper out! Here me and Erwin Tanin, a PhD student at Johns Hopkins, calculated a new upper limit on how much our observable universe could have expanded during an event called cosmic inflation. A preprint is available here: <LINK> 1/n <LINK> Cosmic inflation, an era of accelerated expansion of the universe before the Big Bang epoch, generates gravitational waves which propagate through the space. 2/n If the energy these gravitational waves carry was too high, they would mess up the formation of lights elements (the so-called Big Bang Nucleosynthesis or BBN), so that the amount of observed elements would not match to the amount predicted from theory. 3/n The energy of gravitational waves at the time of BBN is not known but one can calculate that if the universe expanded in some funny way between inflation and BBN, it is bigger than what one would normally expect. 4/n By using the limits on the amount of gravitational waves at the time of BBN, we infer an upper limit on how much the universe could have expanded between end of inflation and BBN - and how much during inflation itself. 5/n We also showed that even the most optimistic future ground- or space-based gravitational wave observatories are unlikely to be able to improve this limit. 6/n All in all, this was a nice project which I enjoyed a lot. This was also a new opening for me, as I had not really worked on gravitational waves before. It was great and a lot of fun to learn new things. Hope you'll like the outcome! 7/7",https://arxiv.org/abs/2004.10702,"Gravitational waves (GW) produced in the early Universe contribute to the number of relativistic degrees of freedom, $N_{\rm eff}$, during Big Bang Nucleosynthesis (BBN). By using the constraints on $N_{\rm eff}$, we present a new bound on how much the Universe could have expanded between horizon exit of the largest observable scales today and the end of inflation. We discuss the implications on inflationary models and show how the new constraints affect model selection. We also discuss the sensitivities of the current and planned GW observatories such as LIGO and LISA, and show that the constraints they could impose are always less stringent than the BBN bound. ",Gravitational wave constraints on the observable inflation,7,"['A new paper out! Here me and Erwin Tanin, a PhD student at Johns Hopkins, calculated a new upper limit on how much our observable universe could have expanded during an event called cosmic inflation. A preprint is available here: <LINK> 1/n <LINK>', 'Cosmic inflation, an era of accelerated expansion of the universe before the Big Bang epoch, generates gravitational waves which propagate through the space. 2/n', 'If the energy these gravitational waves carry was too high, they would mess up the formation of lights elements (the so-called Big Bang Nucleosynthesis or BBN), so that the amount of observed elements would not match to the amount predicted from theory. 3/n', 'The energy of gravitational waves at the time of BBN is not known but one can calculate that if the universe expanded in some funny way between inflation and BBN, it is bigger than what one would normally expect. 4/n', 'By using the limits on the amount of gravitational waves at the time of BBN, we infer an upper limit on how much the universe could have expanded between end of inflation and BBN - and how much during inflation itself. 5/n', 'We also showed that even the most optimistic future ground- or space-based gravitational wave observatories are unlikely to be able to improve this limit. 6/n', ""All in all, this was a nice project which I enjoyed a lot. This was also a new opening for me, as I had not really worked on gravitational waves before. It was great and a lot of fun to learn new things. Hope you'll like the outcome! 7/7""]",20,04,1504