sp000010"><strong class="boldFont">Theorem 1.strong>If <span id="mmlsi3" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si3.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=759b670fd02ad6fbfdf850c8dffbb43e" title="Click to view the MathML source">Dspan><span class="mathContainer hidden"><span class="mathCode">span>span>span>has <span id="mmlsi4" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si4.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=a9296249511d5c96b9f1990863714afa" title="Click to view the MathML source">Pspan><span class="mathContainer hidden"><span class="mathCode">span>span>span>-property, then <span id="mmlsi3" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si3.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=759b670fd02ad6fbfdf850c8dffbb43e" title="Click to view the MathML source">Dspan><span class="mathContainer hidden"><span class="mathCode">span>span>span>is a ball.
sp000015">Four equivalent formulations of the Pompeiu problem are discussed.
sp000020">A domain <span id="mmlsi3" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si3.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=759b670fd02ad6fbfdf850c8dffbb43e" title="Click to view the MathML source">Dspan><span class="mathContainer hidden"><span class="mathCode">span>span>span> has <span id="mmlsi4" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si4.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=a9296249511d5c96b9f1990863714afa" title="Click to view the MathML source">Pspan><span class="mathContainer hidden"><span class="mathCode">span>span>span>-property if there exists an <span id="mmlsi8" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si8.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=d4d9918164982e3b1811bbf40f7e17da" title="Click to view the MathML source">f≠0span><span class="mathContainer hidden"><span class="mathCode">span>span>span>, <span id="mmlsi9" class="mathmlsrc">source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si9.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=0c081304b01d7cef1b163e768979b9c5">ss="imgLazyJSB inlineImage" height="18" width="77" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0893965916302099-si9.gif">
sp000025">The result obtained concerning the related symmetry problem is:
sp000030"><strong class="boldFont">Theorem 2.strong>If <span id="mmlsi14" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si14.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=45b5868e95f9e764e0ec96deecfd6e21" title="Click to view the MathML source">(∇<sup>2sup>+k<sup>2sup>)u=0span><span class="mathContainer hidden"><span class="mathCode">span>span>span>in <span id="mmlsi3" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si3.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=759b670fd02ad6fbfdf850c8dffbb43e" title="Click to view the MathML source">Dspan><span class="mathContainer hidden"><span class="mathCode">span>span>span>, <span id="mmlsi16" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si16.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=a03ab6f81914b0e5ec97c0ea404304bb" title="Click to view the MathML source">u∣<sub>Ssub>=1span><span class="mathContainer hidden"><span class="mathCode">span>span>span>, <span id="mmlsi17" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si17.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=5114279c917d214a7a06c281d58a5e4f" title="Click to view the MathML source">u<sub>Nsub>∣<sub>Ssub>=0span><span class="mathContainer hidden"><span class="mathCode">span>span>span>, and <span id="mmlsi18" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si18.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=7493ddd2a1d104f249f654e22d23e8ab" title="Click to view the MathML source">k>0span><span class="mathContainer hidden"><span class="mathCode">span>span>span>is a constant, then <span id="mmlsi3" class="mathmlsrc"><span class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0893965916302099&_mathId=si3.gif&_user=111111111&_pii=S0893965916302099&_rdoc=1&_issn=08939659&md5=759b670fd02ad6fbfdf850c8dffbb43e" title="Click to view the MathML source">Dspan><span class="mathContainer hidden"><span class="mathCode">span>span>span>is a ball.