A bstractIn the (" 1 " 2 ) 2 {approxi m ati on the C asi m i renergy ofa di l ute di el ectri c bal l i s deri ved usi ng a si m pl e and cl ear m ethod of the m ode sum m ati on. T he addi ti on theorem for the B esselfuncti ons enabl es one to present i n a cl osed form the sum over the angul ar m om entum before the i ntegrati on over the i m agi nary frequenci es. T he l i near i n (" 1 " 2 ) contri buti on i nto the vacuum energy i s rem oved by an appropri ate subtracti on. T he rol e of the contact term s used i n other approaches to thi s probl em i s el uci dated. 12. 20. D s,03. 70. + k,78. 60. M q,42. 50. Lc Typeset usi ng R EV T E X
I. IN T R O D U C T IO NT he progress i n cal cul ati on ofthe C asi m i r energy i s rather sl ow . In hi s pi oneer paper [ 1]i n 1948 H .B.G .C asi m i r cal cul ated the vacuum el ectrom agneti c energy for the m ost si m pl e boundary condi ti ons,for two paral l elperfectl y conducti ng pl ates pl aced i n vacuum . D i el ectri c properti esofthe m edi a separated by pl ane boundari esdo notadd new m athem ati caldi cul ti es [ 2] . H owever the rst resul t on the cal cul ati on ofthe C asi m i r energy for the non-at boundari es was obtai ned onl y i n 1968. By com puter cal cul ati ons,l asted 3 years, T .H .Boyer found the C asi m i r energy ofa perfectl y conducti ng spheri calshel l [ 3] . A ccount ofdi el ectri c and m agneti c properti es ofthe m edi a i n cal cul ati ons ofthe vacuum energy for non at i nterface l eads to new pri nci paldi cul ti es or,m ore preci sel y,to a new structure of di vergenci es.T he cal cul ati on ofthe C asi m i r energy i n a speci alcase,w hen both the m ateri alm edi a have the sam e vel oci ty ofl i ght,proves to be,from the m athem ati calstand poi nt,exactl y the sam e as for perfectl y conducti ng shel l s pl aced i n vacuum and havi ng the shape ofthe i nterface between these m edi a [ 4{14] .T he rst attem pt to cal cul ate the C asi m i r energy ofa di el ectri c com pact bal lhas been undertaken by K .A .M i l ton i n 1980 [ 15] .A nd onl y justrecentl y thevacuum el ectrom agneti c energy ofa di l ute di el ectri c bal lwas found 1 [ 16{20] . T he l i ght vel oci ty i s di sconti nuous on the surface of such a bal l . In R ef.[ 21]the anal ysi s of the di vergenci es, w hi ch appear i n cal cul ati on ofthe C asi m i r energy ofa di el ectri c bal l ,has been carri ed out by determ i ni ng the rel evant heat kernelcoe ci ents. T he rol e of di spersi on i n thi s probl em i s now under study al so [ 8, 19, 22{25] .U nder these ci rcum stances i t i s of a i ndubi tabl e i nterest to devel op new m ethods for cal cul ati ng the vacuum energy fornon-atboundari esw i th al l owance forthe m ateri alcharacteri sti cs ofthe m edi a. It i s thi s ai m that i s pursued i n the present paper.Practi cal l y al lthe cal cul ati ons ofthe C asi m i r energy for the boundari es w i th spheri cal orcyl i ndri calsym m etri es use the uni form asym ptoti c expansi on forthe Besselfuncti ons. In pl ace ofthi s we are em pl oyi...