KDK@65 - Abstracts

The good old times

Bernard Schutz

My (Brilliant) Greek Friend

Kostas Kokkotas came to me in Cardiff just to do a Master’s degree. After that he returned to Thessaloniki for his PhD. But his time in Cardiff has led to a life-long professional relationship and friendship. In this talk I will reflect upon the interwoven strands of our friendship and our working relationship, including our work on w-modes and then his later research and his impact on our field. They are interwoven because they are not really separable: to work with Kostas is to be his friend!

Massimo Tinto

Reminiscences of a Gravitational Wave Physicist. II: When, Where, What, Who, How…….did all that happen?

It was (almost) exactly 40 years ago when I first met Kostas. That happened at the 1984 Gregynog meeting organized by our research supervisor, Professor Bernard F. Schutz. Although Kostas and I never published any joint articles, the scientific and social interactions we were used to have at Cardiff made us remain friends to this day!

As I am preparing my presentation and remembering those challenging and yet exciting days, I feel very proud thinking how persistent and brave (and visionary?) we were back then. So, let me go back in time and share with you my memories.

Andrzej Krolak

Kostas: A Tapestry of Memories

I first met Kostas in Cardiff in February 1987 when I began my postdoctoral fellowship with Bernard Schutz. Over the years, we interacted on numerous occasions through mutual visits, his participation in a conference I organized in Warsaw, and joint visits to Jena and Potsdam. Additionally, we collaborated at schools in Bad Honnef. Our collaboration on gravitational wave data analysis from compact binary sources started in the early 1990s, resulting in several co-authored papers.

In this presentation, I will share the history of our decades-long acquaintance, detailing the research we conducted on compact binary coalescence (CBC) data analysis. I will also discuss my recent work on post-merger signals from binary neutron star mergers.

Yasufumi Kojima

Bursts on a compact star

Kostas’ first paper was a new oscillation mode accompanied with gravitational waves, and it inspired my research work. Since then, I have been interested in his work. I am going to talk about a few topics on burst events on a compact star.

The middle ages

Gabrielle Allen and Ed Seidel

Kostas and the EU Astrophysics Network

We provide insight on the long and profound influence that Kostas had on many of us in our careers and in our lives. In particular, we will provide an overview of the EU Network project in which Kostas played an important role. The European Network on Sources of Gravitational Waves (2000-2003) project helped build the European Gravitational Wave community and software infrastructure that are still contributing today.

Luciano Rezzolla

A shared love: compact stars

The study of compact stars has been at the heart of Kostas' work for almost 40 years. I will discuss the recent progress made in modelling these objects and our present understanding about their equation of state, their structure, and maximum mass.

Ulrich Sperhake

Gravitational waves beyond general relativity and the standard model

General relativity (GR) and the standard model (SM) or particle physics are the main pillars of our contemporary framework of theoretical physics. Despite the tremendous success of this GR+SM paradigm, there is mounting evidence -- theoretical and observational -- that the GR+SM paradigm needs to be extended. The new era of gravitational-wave (GW) observations provides unprecedented opportunities to explore physics beyond GR+SM, but this GW-guided quest for new physics critically relies on the availability of concrete and accurate theoretical predictions for the expected GW signals. We present such modeling results for two specific scenarios, stellar collapse in scalar-tensor gravity and the inspiral, merger and ringdown of boson-star binaries. We furthermore explore how these system's signatures may show up in GW observations.

Hajime Sotani

Asteroseismology and collaboration with Kokkotas-san

Since I met Kostas in January 2004, I have continuously collaborated on several projects with him up to now. In particular, I could research in a wonderful environment in the period from 2006 to 2010, in which Kostas hired me. In this presentation, I will talk about the neutron star oscillations in scalar-tensor gravity, magnetar oscillations, and crustal torsional oscillations, which are the main achievements obtained from the collaboration, and also show some good memories of Kostas.

The decline

Daniela Doneva & Stoytcho Yazadjiev

Neutron star in modified gravity - structure and dynamics

Neutron stars provide a rich laboratory for testing not only the behavior of matter at extreme densities but also strong gravity. We will review some interesting models of neutron stars in extended scalar-tensor theories. Their dynamics and strategies to test them astrophysically will also be discussed. These were some of the main topics on which we collaborated with Kostas.

Arthur Suvorov

Dynamical tides and GRB precursors

Strong tidal fields develop in the moments leading up to binary mergers involving at least one neutron star. These tides excite internal fluid motions -- described as a set of forced quasi-normal modes (QNMs) -- to a degree which depends on the mutual separation, equations of state, spins, magnetic fields, and so on. In the context of Kostas' long history in developing the theory of QNMs, I will describe not only some mathematical and numerical techniques we have worked on together that can be used to evolve the binary inspiral and mode spectra/amplitudes simultaneously, but also the observational landscape. Can these modes grow to large enough amplitudes to "break" the crust? What happens if they do? How is the inspiral accelerated in either case? I'll describe the last few years of work together with Kostas and others in these directions.

Sebastian Völkel

Echoes from the past to the present

In this talk, I will sketch Kostas' pioneering contributions to gravitational wave echoes from ultra compact objects. I will then outline how this field entered a phase of exponential growth of publications about 20 to 30 years later, and how Kostas' interest in these aspects returned and he "trapped" me into it. Although no evidence for their discovery can be found in the overall literature, there are interesting recent extensions to analog gravity systems that will be discussed.

The greek connection

Thomas Sotiriou

TBA

Kyriakos Destounis

"The balance between chaos and order": A postdoc's tale

In this talk, I will recollect some of my scientific and social endeavours from 2019 to 2022 when I was a postdoctoral fellow in Tuebingen under the supervision of Prof. Kostas Kokkotas. From a scientific point of view, I will focus on some research aspects that I endured together with Kostas and collaborators, such as the gravitational-wave imprints of chaotic extreme-mass-ratio inspirals. Most importantly, from a social point of view, I will recall pleasant memories and anecdotes from my day-to-day life with Kostas, as well as other facets of our interaction with the enigmatic, though amusing ('Greek-definite'), social environment of the city of Tuebingen.

Nick Stergioulas

TBA