We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure [email protected]
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 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.
Ramsey’s theorem asserts that every k-coloring of
$[\omega ]^n$
admits an infinite monochromatic set. Whenever
$n \geq 3$
, there exists a computable k-coloring of
$[\omega ]^n$
whose solutions compute the halting set. On the other hand, for every computable k-coloring of
$[\omega ]^2$
and every noncomputable set C, there is an infinite monochromatic set H such that
$C \not \leq _T H$
. The latter property is known as cone avoidance.
In this article, we design a natural class of Ramsey-like theorems encompassing many statements studied in reverse mathematics. We prove that this class admits a maximal statement satisfying cone avoidance and use it as a criterion to re-obtain many existing proofs of cone avoidance. This maximal statement asserts the existence, for every k-coloring of
$[\omega ]^n$
, of an infinite subdomain
$H \subseteq \omega $
over which the coloring depends only on the sparsity of its elements. This confirms the intuition that Ramsey-like theorems compute Turing degrees only through the sparsity of its solutions.
Recommend this
Email your librarian or administrator to recommend adding this to your organisation's collection.