MathOverflow will be down for maintenance for approximately 3 hours, starting Monday evening (06/24/2013) at approximately 9:00 PM Eastern time (UTC-4).
show/hide this revision's text 6 corrected spelling of "Hausdorff"

There is a Haussdorff Hausdorff gap, a sequence $\{f_\alpha,g_\alpha:\alpha\lt\omega_1\}$ of $\omega\to\omega$ functions such that $f_\alpha\lt^*f_\beta<^*g_\beta<^*g_\alpha$ hold for $\alpha\lt\beta\lt\omega_1$ (here $f\lt^* g$ denotes eventual dominance, i.e., that $f(n)\lt g(n)$ holds for large $n\lt\omega$) and there is no function $f:\omega\to\omega$ such that $f_\alpha\lt^* f\lt^* g_\alpha$ holds for $\alpha\lt\omega_1$. If we identify the reals with ${}^\omega\omega$ and set $H_\alpha=\{f:f_\alpha\lt^* f \lt^* g_\alpha\}$ then $\{H_\alpha:\alpha\lt\omega_1\}$ is a decreasing sequence of nonempty $F_\sigma$ with empty intersection.

show/hide this revision's text 5 Replaced < with \lt

There is a Haussdorff gap, a sequence $\{f_\alpha,g_\alpha:\alpha<\omega_1\}$\{f_\alpha,g_\alpha:\alpha\lt\omega_1\}$ of $\omega\to\omega$ functions such that $f_\alpha<^*f_\beta<^*g_\beta<^*g_\alpha$ f_\alpha\lt^*f_\beta<^*g_\beta<^*g_\alpha$ hold for $\alpha<\beta<\omega_1$ \alpha\lt\beta\lt\omega_1$ (here $f<^* f\lt^* g$ denotes eventual dominance, i.e., that $f(n)$H_\alpha=\{f:f_\alpha<^* f(n)\lt g(n)$ holds for large $n\lt\omega$) and there is no function $f:\omega\to\omega$ such that $f_\alpha\lt^* f\lt^* g_\alpha$ holds for $\alpha\lt\omega_1$. If we identify the reals with ${}^\omega\omega$ and set $H_\alpha=\{f:f_\alpha\lt^* f <^* \lt^* g_\alpha\}$ then $\{H_\alpha:\alpha<\omega_1\}$\{H_\alpha:\alpha\lt\omega_1\}$ is a decreasing sequence of nonempty $F_\sigma$ with empty intersection.

show/hide this revision's text 4 Rollback to Revision 1

There is a Haussdorff gap, a sequence $\{f_\alpha,g_\alpha:\alpha<\omega_1\}$ of $\omega\to\omega$ functions such that $f_\alpha<^*f_\beta<^*g_\beta<^*g_\alpha$ hold for $\alpha<\beta<\omega_1$ (here $f<^* g$ denotes eventual dominance, i.e., that $f(n)

If we identify the reals with ${}^\omega\omega$ and set $H_\alpha=\{f:f_\alphaf(n)$H_\alpha=\{f:f_\alpha<^* f <^* g_\alpha\}$ then $\{H_\alpha:\alpha<\omega_1\}$ is a decreasing sequence of nonempty $F_\sigma$ sets with empty intersection.

THE PROGRAM LEAVES OUT HALF OF MY ANSWER!

show/hide this revision's text 3 added 64 characters in body
show/hide this revision's text 2 added 13 characters in body
show/hide this revision's text 1