Search Talks

In this talk, I will discuss my exploration of the gravothermal collapse of isolated self-interacting dark matter (SIDM) halos, driven deep into the core-collapsed regime where interactions are frequent. We investigate how elastic collisions influence the central region of SIDM halos as they undergo core collapse. In our numerical findings, we discover a remarkable universality in the behavior of halos, allowing us to predict their evolution deep in the core-collapsed regime. We develop a semi-analytic method to characterize the core properties of the halo in the latest stages of evolution, which is crucial for making predictions of the mass of potential black holes forming at the heart of these dark matter halos.

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In my talk I will review motivation for and construction of an infinite derivative gravity. Especially a connection to the string field theory will be highlighted. Then I will demonstrate an exact embedding of the Starobinsky inflation in this construction. In final part I will speak about modifications to observable compared to local models of inflation: spectral indexes, tensor/to scalar ratio, shapes of non-gaussianities and related parameters, gravitational waves production.

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Recent developments point to a remarkable resistance of black holes to tidal deformations under the influence of external gravitational fields. Relying on hidden symmetries, compelling progress has been achieved to explain that the Love numbers, characterizing tidal deformations for Kerr black holes, vanish. How does the phenomenon of tidal squeezing manifest in broader dynamical contexts? An examination of the dynamical tidal deformations in rotating black holes will be presented.

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When additional degrees of freedom are considered during inflation, a crucial aspect of early universe physics emerges: the generation of isocurvature quantum fluctuations. In this talk, we will present generation and detection forecast for axionic blue-tilted isocurvature power spectra. The large blue-tilt readily evades current CMB bounds. Following a brief review, we will discuss a SUSY-embedded axion model which generates a strongly blue tilted (nI~4) isocurvature spectrum during inflation when the quantum modes are starting to be underdamped ( m/H > 3/2 ). Interestingly, there exist parametric regions with strong resonant spectral behavior that lead to rich isocurvature spectral shapes and large amplitude enhancements. These can be particularly interesting with observational consequences, in relation to the generation of PBH and GWs. The isocurvature spectral tilt is directly linked to the axion mass during inflation. Detecting blue-tilted isocurvatures can offer indirect evidence of a weakly interacting dark matter-like spectator field beyond conventional thermal-relic scenarios. Lastly, we will examine and forecast constraints for experiments such as Euclid (upcoming) and MegaMapper (proposed) using EFTofLSS based perturbative techniques. In the process we will comment upon the consistent renormalization requirements for mixed adiabatic and blue isocurvature primordial spectra.

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The Hitchin systems are a remarkable family of integrable models associated to the moduli space of principal bundles on a compact Riemann surface. In this talk, I explain how the loop group uniformization of this moduli space can be used to construct an r-matrix for the Hitchin systems. This r-matrix has been previously used in the description of the Friedan-Schenker connection on the space of conformal blocks.

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Nonclassical causal modeling was developed in order to explain violations of Bell inequalities while adhering to relativistic causal structure and faithfulness -- that is, avoiding fine-tuned causal explanations. Recently, a no-go theorem stronger than Bell's theorem has been derived, based on extensions of Wigner's friend thought experiment: the Local Friendliness (LF) no-go theorem. Here we show that the LF no-go theorem poses formidable challenges for the field of causal modeling, even when nonclassical and/or cyclic causal explanations are considered. We first recast the LF inequalities, one of the key elements of the LF no-go theorem, as special cases of monogamy relations stemming from a statistical marginal problem; we then further recast LF inequalities as causal compatibility inequalities stemming from a nonclassical causal marginal problem, for a causal structure implied by well-motivated causal-metaphysical assumptions. We find that the LF inequalities emerge from the causal modeling perspective even when allowing the latent causes of observed events to admit post-quantum descriptions, such as Generalised Probabilistic Theories (GPT) or even more exotic theories. We further prove that no nonclassical causal model can explain violations of LF inequalities without violating the No Fine-Tuning principle. Finally, we note that these obstacles cannot be overcome even if one were to appeal to cyclic causal models.

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“Saturons" are macroscopic objects that saturate the field theoretic upper bound on microstate degeneracy. Due to their maximal microstate entropy, from a quantum information perspective, saturons and black holes belong to the same universality class with common key properties.  However, as opposed to black holes,  saturons do not require gravity and can emerge via ordinary renormalizable interactions, such as QCD, in the form  of soliton-like states. Due to this feature, saturons serve as laboratories for understanding certain properties of black holes. After reviewing the general properties of saturons, we discuss their implications for fundamental physics and cosmology. In particular, we explain how saturons can lead to a new form of phase transition. 

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Studying galaxy evolution is a human endeavour.  Simulations would ideally include physical models based on relevance, but we are often limited by practical considerations like CPU time and code complexity. I will examine energy inputs to galaxies from radiation and stellar feedback, how they are modeled in simulations, and where they are expected to influence the state of the gas and the overall evolution of a galaxy. I will focus on superbubbles (clustered supernova and stellar wind feedback) and local radiation fields, looking at the differences in what these feedbacks can do in terms of where they act in the galaxy, how that impact changes over cosmic time and how the limitations of simulations have affected our view of them.

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