BEGIN:VCALENDAR
VERSION:2.0
METHOD:PUBLISH
CALSCALE:GREGORIAN
PRODID:-//WordPress - MECv7.32.0//EN
X-ORIGINAL-URL:https://www.cmm.uchile.cl/
X-WR-CALNAME:CMM
X-WR-CALDESC:Centro de Modelamiento Matemático
X-WR-TIMEZONE:America/Santiago
BEGIN:VTIMEZONE
TZID:America/Santiago
X-LIC-LOCATION:America/Santiago
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0400
TZNAME:-04
DTSTART:20260902T112259
END:STANDARD
END:VTIMEZONE
REFRESH-INTERVAL;VALUE=DURATION:PT1H
X-PUBLISHED-TTL:PT1H
X-MS-OLK-FORCEINSPECTOROPEN:TRUE
BEGIN:VEVENT
CLASS:PUBLIC
UID:MEC-334b7ca6dff862006c643f51a750eaaa@cmm.uchile.cl
DTSTART;TZID=America/Santiago:20260827T103000
DTEND;TZID=America/Santiago:20260827T120000
DTSTAMP:20260825T115739Z
CREATED:20260825
LAST-MODIFIED:20260826
PRIORITY:5
SEQUENCE:2
TRANSP:OPAQUE
SUMMARY:Graph Theory Seminar “Ramsey numbers of expansion hypertrees”
DESCRIPTION:Abstract: Given a $k$-uniform hypergraph $H$, the Ramsey number $R(H)$ is the smallest $N$ such that every $2$-colouring of the edges of $K_N^{(k)}$ contains a monochromatic copy of $H$. For graphs, Burr gave two constructions bounding $R(T)$ from below for a tree $T$, and his formula is now known to be exact for trees of small maximum degree. In the hypergraph setting, almost nothing is known beyond loose paths and cycles.\nWe study $R(T^{(k)})$, where $T^{(k)}$ is the $k$-expansion of a tree $T$, obtained by adding $k-2$ new vertices to each edge. We show that for bounded-degree trees the Ramsey number is at most $(1+\eta)\frac{1}{2}(2k-1)n$, and we prove a general lower bound $R(H) \geq |V(H)| + \tau(H) – 1$ for connected $k$-graphs $H$, where $\tau$ is the vertex cover number. These bounds are asymptotically tight for loose paths. In this talk, we will see how Burr's constructions generalise to the hypergraph setting, what the resulting lower bound looks like for expansions, and discuss the conjectures this work suggests.\nSpeaker: Vicente Sandoval (DIM, U. Chile)\n
URL:https://www.cmm.uchile.cl/events/graph-theory-seminar-ramsey-numbers-of-expansion-hypertrees/
ORGANIZER;CN=CMM:MAILTO:
CATEGORIES:Seminarios
LOCATION:Sala John Von Neumann, 7th floor, Beauchef 851
ATTACH;FMTTYPE=image/jpeg:https://www.cmm.uchile.cl/wp-content/uploads/2026/05/Optimizacion-y-equilibrio.jpg
END:VEVENT
END:VCALENDAR