Published online by Cambridge University Press: 20 January 2009
In a very remarkable work on the operational Calculus, Dr Balth. van der Pol has introduced a new function, playing with respect to Bessel function of order zero the same part as the cosine- or sine-integral with respect to the ordinary cosine or sine. He showed that this function—which he called Bessel-integral junction—can be used to express the differential coefficient of any Bessel function with respect to its index. But he did not investigate the further properties of his new function. I propose to give here some of them, which appear to be interesting, and to introduce and study the functions connected, in the same way, with Bessel functions of any order.
page 276 note 1 Philosophical Magazine, 8 (1929), 861–898, (887).Google Scholar
page 276 note 2 For properties of cosine- and sine-integrals, the reader is referred to Nielsen, Niels, Theorie des Integrallgarithmus (Leipzig, 1906). Nielsen's notation will be used through this paper. As regards Bessel functions, we shall follow Watson's notation.Google Scholar
page 276 note 3 Dr van der Pol uses the simple notation Ji (x). As we shall deal with functions connected with the Bessel function of order n, we find it convenient to denote van der Pol's function by Ji 0(x), thus introducing the order of Bessel-integral functions.
page 284 note 1 The third of these formulae is given in Nielsen's book with a slight mistake: he wrote instead of
which is the real value.
To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your Dropbox account. Find out more about saving content to Dropbox.
To save this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your Google Drive account. Find out more about saving content to Google Drive.