Since the discovery of the first binary black-hole merger in 2015, analytical and numerical solutions to the relativistic two-body problem have been essential for the detection and interpretation of nearly 100 gravitational waves from compact-object binaries. Future experiments will detect black holes at cosmic dawn, probe the nature of gravity, and reveal the composition of neutron stars with...
The Event Horizon Telescope images of M87 and Sgr A have
opened a new era of resolved imaging of black holes at the event
horizon scale. I will describe how EHT measurements are made,
how they can be interpreted with the aid of state-of-the-art models,
what they teach us about black holes, and what the prospects are for
future experiments.
In this talk I will discuss the discovery of the Fast Radio Bursts (FRBs), short, millisecond-duration bursts of radio emission bright enough to be seen at cosmological distances. The discovery of FRBs was serendipitous, but not unlike the discovery of pulsars some 40 years prior. It took many years for FRBs to be accepted as true celestial objects but today they are valuable cosmological...
The orbit of the S2 star and event horizon scale imaging have provided the strongest evidence yet that supermassive black holes (SMBHs) exist at the Galactic Center and in M87. Neither technique, however, can be easily applied beyond these two galaxies. Instead, direct evidence for other SMBHs in the nearby Universe has relied on measurements and modeling of spatially resolved kinematics of...
Galactic nuclei are the densest stellar environments in the Universe, and their gravitational blenders produce frequent close encounters between combinations of stars and compact objects. These encounters, in turn, lead to a wide variety of transients. Some of these transients are electromagnetically luminous, such as tidal disruption events, quasi-periodic eruptions, and stellar collisions....
Announcing the dawn of a new era of multi-messenger astrophysics, the gravitational wave event GW170817 – involving the collision of two neutron stars – was detected in 2017. In addition to the gravitational wave signal, it was accompanied by electromagnetic counterparts providing new windows into the different physics probed by the system. Since then, several gravitational wave events...
In June 2023, pulsar-timing array experiments across the world announced evidence for correlations in the timing properties of millisecond pulsars scattered across the Milky Way. The signature of these correlations is consistent with an all-sky, broadband, background of gravitational waves at nanohertz frequencies, washing through the Galaxy. I will present the analyses that led to these...
In the talk, we will present the results of high precision pulsar timing of 57 millisecond pulsars conducted using the the Chinese FAST 500-meter radio telescope. Particularly, we will highlight the gravitational wave searching efforts of the Chinese Pulsar Timing Array collaboration. More backgrounds and topics on pulsar timing, nanoHertz GW detection, and gravity test will be also covered....
I will review developments in the study of relativistic stellar explosions, systems in which a newborn compact object drives a transient powerful outflow. For decades, the only firmly established example was long‐duration gamma‐ray bursts, thought to represent the special case of a narrow ultra‐relativistic jet lasting seconds. However, in recent years the landscape has broadened dramatically...
Most of the observable matter in the Universe is in the form of plasma, or tenuous ionized gas, and the complicated behavior of plasmas underlies many processes in astrophysics. Plasmas interact with electromagnetic fields, display collective effects and instabilities, and can, under certain conditions, accelerate particles far out of thermal equilibrium. Plasmas are also responsible for...
A gigantic bubble of γ-rays with energies up to 2 PeV is detected by LHAASO in the Cygnus region. It implies the existence of a CR accelerator in the core of the bubble which is continuously injecting CR particles with energies up to few tens of PeV in the ambient HI gas thus emitting the UHE photons. This evidences the galactic origin of CRs above the knee which concentrate towards the core...
Over the recent years, we have witnessed several extraordinary findings in Astrophysics - amongst them the discovery of Ultra High Energy gamma-ray sources, the astronomical objects whose electromagnetic spectra extend beyond 100 TeV. We believe that the discovery of UHE gamma rays should allow us to finally solve the century-old puzzle of the origin of galactic cosmic rays. But the...
The nature of the main ingredients of the standard model of cosmology, dark matter and dark energy, remains a mystery. Better observations are needed, where the biggest advance will come from precise measurements of the growth of large-scale structure. In principle, the next generation of imaging and spectroscopic surveys provide an impressive amount of information about the universe, but...
The nature of dark matter stands as one of the most fundamental mysteries in physics. Numerous theories beyond the Standard Model have postulated the existence of dark matter particles. However, despite extensive research, compelling laboratory evidence has yet to be obtained. In this presentation, I will provide an overview of the global experimental endeavors dedicated to the search for dark...
Title: A minimal SM/LCDM cosmology
Neil Turok, University of Edinburgh and Perimeter Institute
Abstract:
Recent observations point to a surprisingly economical description of the universe on both very small and very large scales. Stimulated by these findings, Boyle and I have proposed a new, potentially more complete theoretical framework than currently popular paradigms. Our search has so...
