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Dy­nam­ic wet­ting

My ac­tive re­search is on the dy­nam­ics of wet­ting. Al­though the field has seen a lot of in­ter­est over the last decades, there is still a wealth of unan­swered ques­tions about which dy­nam­ics dom­i­nate at the triple con­tact line of droplets. This is in part due to the dif­fi­cul­ty of ob­serv­ing mol­e­c­u­lar process­es in reg­u­lar lab­o­ra­to­ry ex­per­i­ments.

Thanks to re­cent de­vel­op­ments of ef­fi­cient mol­e­c­u­lar sim­u­la­tion soft­ware and the in­creased avail­abil­i­ty of suf­fi­cient com­pu­ta­tion­al pow­er, we use mol­e­c­u­lar dy­nam­ics to ob­serve sys­tems of sizes ap­proach­ing mi­crom­e­ter length scales. By mod­el­ing sys­tems which bridge mol­e­c­u­lar and macro­scop­ic physics we can study process­es of wet­ting in great de­tail.

PhD The­sisMol­e­c­u­lar process­es in dy­nam­ic wet­ting

Strong-field QED

Mas­ter’s project, su­per­vised by Dr. An­ton Ilder­ton

For my mas­ter’s project at Umeå Uni­ver­si­ty I stud­ied the quan­tum elec­tro­dy­nam­i­cal (QED) ef­fect of pair an­ni­hi­la­tion in­side ex­treme laser fields. This ef­fect re­lates to the con­stant cre­ation and an­ni­hi­la­tion of vir­tu­al par­ti­cles in space—or, the quan­tum vac­u­um. Since en­er­gy can­not be cre­at­ed from noth­ing, these vir­tu­al par­ti­cles ex­ist only as a short-lived fluc­tu­a­tion. How­ev­er, if dur­ing this short life-span the vir­tu­al pair ab­sorbs the en­er­gy re­quired to cre­ate their mass (E = 2mc2), they can split apart and be­come real par­ti­cles. This phe­nom­e­na is known as Schwinger pair pro­duc­tion and can be ob­served in ex­treme­ly strong elec­tric fields, where an abun­dance of pho­tons are used to pro­vide the re­quired en­er­gy.

Feynman diagrams of strong-field QED processes. Described in figure caption.

Ex­am­ple strong-field QED process­es. A dou­ble line rep­re­sents a par­ti­cle dressed by the pho­ton field (dashed lines). Pic­tured be­low is a Schwinger pair pro­duc­tion event and the one-pho­ton pair an­ni­hi­la­tion chan­nel.

This project stud­ied a sim­i­lar ef­fect, where­in two par­ti­cles in a strong elec­tric field an­ni­hi­late to emit a sin­gle pho­ton—a chan­nel which is nor­mal­ly pro­hib­it­ed, as it vi­o­lates mo­men­tum con­ser­va­tion. How­ev­er, by in­ter­act­ing with some num­ber of pho­tons in­side a back­ground field, the mo­men­tum con­ser­va­tion for the sin­gle-pho­ton emis­sion can be satisi­fied for the par­ti­cle pair.

We cal­cu­lat­ed the chan­nel’s cross sec­tion for two mod­ern, ex­treme­ly pow­er­ful laser fa­cil­i­ties: the Eu­ro­pean XFEL and ELI in­fra­struc­tures. We found that the chan­nel should be present in the XFEL field un­der very fine­ly tuned ex­per­i­men­tal set-ups, but that it is not vis­i­ble at the ELI sites.

The­sisPair an­ni­hi­la­tion in a laser pulse

Quan­tum plas­mas

Bach­e­lor’s project, su­per­vised by Dr. Jens Za­man­ian

In quan­tum physics, a par­ti­cle’s spin leads to many in­ter­est­ing phe­nom­e­na. One such is spin–or­bit cou­pling, which in an ex­ter­nal field can cause split­ting of en­er­gy lev­els, cre­at­ing a fine struc­ture. My bach­e­lor’s project stud­ied the ef­fect of this on Lang­muir waves in mag­ne­tised plas­mas, fol­low­ing a re­cent­ly de­vel­oped the­o­ry of quan­tum plas­mas.

The­sisCon­tri­bu­tion to spin–or­bit cou­pling …