The holographic principle in quantum gravity

The Holographic Principle conjectures that all information contained within the bulk of spacetime is encoded in its boundary. AdS/CFT is a manifestation of this theory, and it provides a map between a quantum theory of gravity and a non-gravitational quantum field theory. This principle is currently being investigated as it could potentially be the postulate that guides in formulating quantum gravitational theories. In this project, we explored some important aspects of the holographic principle by studying a particular example of the AdS3/CFT2 correspondence, where the 2 dimensional CFT theory is taken to be living on the boundary of AdS3. We then derived some important properties that the CFT2 theory should have to correctly reproduce the same results as quantum gravity in AdS3 spacetime. Most importantly, we computed the central charge, which is an intrinsic quantity pertaining to CFT, by comparing the trace anomalies that arose from the stress tensors of CFT2 and AdS3 at its boundary. This is an important quantity that will help in matching gravitational descriptions to the quantum field theory counterparts, such as recovering the Bekenstein-Hawking black hole entropy from the CFT2's Cardy Formula. Lastly, we studied scalar propagators on BTZ black hole spacetime and matched them to the CFT2 two-point functions, which has a periodicity that captures the Hawking Temperature of the BTZ black hole.Bachelor of Science in Physic

Searching for IceCube sub-TeV neutrino counterparts to sub-threshold Gravitational Wave events

Since the release of the Gravitational Wave Transient Catalogue GWTC-2.1 by the LIGO-Virgo collaboration, sub-threshold gravitational wave (GW) candidates are publicly available. They are expected to be released in real-time as well, in the upcoming O4 run. Using these GW candidates for multi-messenger studies complement the ongoing efforts to identify neutrino counterparts to GW events. This in turn, allows us to schedule electromagnetic follow-up searches more efficiently. However, the definition and criteria for sub-threshold candidates are pretty flexible. Finding a multi-messenger counterpart via archival studies for these candidates will help to set up strong bounds on the GW parameters which are useful for defining a GW signal as sub-threshold, thereby increasing their significance for scheduling follow-up searches. Here, we present the current status of this ongoing work with the IceCube Neutrino Observatory. We perform a selection of the sub-threshold GW candidates from GWTC-2.1 and conduct an archival search for sub-TeV neutrino counterparts detected by the dense infill array of the IceCube Neutrino Observatory, known as "DeepCore". For this, an Unbinned Maximum Likelihood (UML) method is used. We report the 90% C.L. sensitivities of this sub-TeV neutrino dataset for each selected sub-threshold GW candidate, considering the spatial and temporal correlation between the GW and neutrino events within a 1000 s time window

An improved mapping of ice layer undulations for the IceCube Neutrino Observatory

A precise understanding of the optical properties of the instrumented Antarctic ice sheet is crucial to the performance of the IceCube Neutrino Observatory, a cubic-kilometer Cherenkov array of 5,160 digital optical modules (DOMs) deployed in the deep ice below the geographic South Pole. We present an update to the description of the ice tilt, which describes the undulation of layers of constant optical properties as a function of depth and transverse position in the detector. To date, tilt modeling has been based solely on stratigraphy measurements performed by a laser dust logger during the deployment of the array. We now show that it can independently be deduced using calibration data from LEDs located in the DOMs. The new fully volumetric tilt model not only confirms the magnitude of the tilt along the direction orthogonal to the ice flow obtained from prior dust logging, but also includes a newly discovered tilt component along the flow

From PeV to TeV: Astrophysical Neutrinos with Contained Vertices in 10 years of IceCube Data

The IceCube Neutrino Observatory is a cubic-kilometer Cherenkov detector at the South Pole, designed to study neutrinos of astrophysical origin. We present an analysis of the Medium Energy Starting Events (MESE), which is a veto-based event selection that selects neutrinos from a background of cosmic rays. This is an extension of the High Energy Starting Event (HESE) analysis, which established the existence of high-energy neutrinos of astrophysical origin. The HESE sample is consistent with a single power law spectrum with best-fit index 2.87+0.20-0.19, which is softer than complementary IceCube measurements of the astrophysical neutrino spectrum. While HESE is sensitive to neutrinos above 60 TeV, MESE improves the sensitivity to lower energies, down to 1 TeV. In this analysis we use an improved understanding of atmospheric backgrounds in the astrophysical neutrino sample via more accurate modeling of the detector self-veto. A previous measurement with a 2-year MESE dataset had indicated the presence of a possible 30 TeV excess. With 10 years of data, we have a larger sample size to investigate this excess. We will use this event selection to measure the cosmic neutrino energy spectrum over a wide energy range. The flavor ratio of astrophysical neutrinos will also be discussed

Search for high-energy neutrino emission from hard X-ray AGN with IceCube

Active Galactic Nuclei (AGN) are powerful astronomical objects with very high luminosities. Theoretical arguments suggest that these objects are capable of accelerating particles to energies of 1020 eV. In environments with matter or photon targets, cosmic-ray interactions transpire leading to the production of pionic gamma rays and neutrinos. Since the AGN environment is rich in gas, dust and photons, they are promising candidate sources of high-energy astrophysical neutrinos. While the neutrinos manage to escape, the gamma rays may further interact and cascade down to hard X-rays in environments with sufficiently large photon or gas targets. We have used 12 years of IceCube data to perform a stacked search and a point source search for high-energy neutrino emission from hard X-ray AGN sampled from Swift-BAT Spectroscopic Survey (BASS) and present the results of these two analyses