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September[0]=["05","All","HEAP","Jamboree","We ask each of the faculty members, postdocs, and students to submit one slide on their recent or ongoing research or on their research interests. The seminar will be composed of 1-2min talks by everyone (a.k.a. machine gun talks or lightning talks). This provides an opportunity for people to know the current activities in the astronomy and high-energy groups, and it also serves as an introduction of the groups to the newly coming students.","Local","","",""]
September[1]=["12","David Neilsen","BYU","The Exciting New Frontier of Gravitational Wave Astronomy","Gravitational waves produced in the merger of two black holes were first detected (almost) exactly four years ago, in September 2015. Since that time, gravitational waves from ten other events have been confirmed, and new detections are now being made almost weekly. Gravitational waves provide a new way to learn about black holes, neutron stars, and cosmology. I will talk about some of the new insights we have learned from gravitational waves, the future of gravitational wave astronomy, and my current work on Dendro-GR. Dendro-GR is a new code for studying black holes and neutron stars that is being developed at BYU and the University of Utah. It combines both fine-scale refinement with highly efficient parallelization to study problems on the next frontier for numerical relativity.","John Belz","","",""]
September[2]=["19","Peng Kian Tan","Singapore","Temporal Intensity Interferometry","Light from thermal blackbody radiators such as stars exhibits photon bunching behavior at sufficiently short timescales. However, with available detector bandwidths, this bunching signal is difficult to observe directly. By performing narrow-band spectral filtering on Sunlight and using actively quenched avalanche photodiodes, we measured an averaged photon bunching signal of g(2)(τ=0) = 1.693 ± 0.003 from the Sun, consistently throughout the day despite fluctuating weather conditions, cloud cover and elevation angle. This demonstrates the robustness of the intensity interferometry technique against atmospheric turbulence and opto-mechanical instabilities, and hence the feasibility to implement measurement schemes with both large baselines and long integration times. We also measured the resultant g(2)(τ) from admixtures of incoherent thermal light with coherent laser light.","Stephan LeBohec","","",""]
September[3]=["20","Federico Urban","CEICO","Ultra Light Dark Matter"," Binary pulsars can very precise detectors for Ultralight Dark Matter: in this talk I will show how we can recover several properties of Dark Matter by looking at secular variations of the binary orbital parameters. As a bonus, I will also discuss a few other fun applications of Pulsar timing data for astronomy and cosmology.
This seminar will be presented as a chalk talk, and should be accessible to both theorists and experimentalists.","John Matthews","Friday 10 AM","",""]
September[4]=["26","Vivienne Baldassare","Yale","Searching for active galactic nuclei in low-mass galaxies with optical photometric variability","The population of massive black holes (BHs) at the centers of nearby low-mass galaxies provides some of the best observational constraints on the masses of “black hole seeds” at high redshift. Furthermore, while BHs are ubiquitous and well-studied in Milky Way-sized and larger galaxies, relatively little is known about the population and properties of BHs in low-mass galaxies. However, BHs in these systems can be difficult to identify due to star formation dilution of the active galactic nucleus (AGN) signal and metallicity effects. I will discuss recent efforts to detect BHs in low-mass galaxies, focusing on searches using optical photometric variability. In Baldassare et al. 2018, we showed that long-term optical variability in low-mass galaxies can identify AGNs missed by other selection techniques. I will present a new analysis of the nuclear variability of more than 50,000 nearby galaxies using data from the Palomar Transient Factory. I will present our sample of low-mass, variability-selected AGNs and discuss implications for the active fraction and occupation fraction at low galaxy stellar masses. I also study the variability properties of AGNs as a function of BH mass down to BH masses of 105 Msun, and find no dependence of variability properties on BH mass.","Anil Seth","","",""]
October[0]=["03","David Nataf","Johns Hopkins","Clues to Globular Cluster Formation","Globular clusters are now well-established to host “Second-generation” stars, which show anomalous abundances in some or all of He, C, N, O, Na, Al, Mg, etc. The simplest explanations for these phenomena typically require the globular clusters to have been ~20× more massive at birth, and to have been enriched by processes which are not consistent with the theoretical predictions of massive star chemical synthesis models. The library of observations is now a vast one, yet there has been comparatively little progress in understanding how globular clusters could have formed and evolved. In this talk I discuss two new insights into the matter. First, I report on a meta-analysis of globular cluster abundances that combined APOGEE and literature data for 42 globular clusters, new trends with globular cluster mass are identified. I discuss the chemical properties of former globular cluster stars that are now part of the field population, and what can be learned. Finally, use updated state-of-the-art massive star stellar evolution models from the Padova group to make predictions for the upcoming and inevitable JWST observations of young globular cluster progenitors in their starburst phase.","Gail Zasowski","","",""]
October[1]=["10","","","No Seminar - Fall Break","","","","",""]
October[2]=["17","Nirmal Raj","TRIUMF","Directional Detection of Dark Matter in Liquid Scintillator Neutrino Experiments","I will show that dark matter with a per-nucleon scattering cross section ≳ 10-28 cm2 could be discovered by liquid scintillator neutrino detectors like BOREXINO, SNO+, and JUNO. Due to the large fluxes admitted, these detectors could find dark matter with masses up to 1021 GeV. I will also show how these detectors could obtain the dark matter velocity distribution by reconstructing the tracks of dark matter scattering on multiple nuclei during transit. This would help to discriminate dark matter signals from potential backgrounds, and to determine the dispersion speed, escape speed, and velocity anisotropies of the local dark matter halo.","Yue Zhao","","",""]
October[3]=["24","Jianhui Lian","Utah","Origin, distribution and evolution of metal elements in the universe","Metal elements (heavier than Hydrogen and Helium) are critical ingredients not only in life on earth but also in almost all astrophysical processes involving baryons, such as star formation, gas cooling, stellar evolution, dust formation, etc. The abundance of these elements provide us an unique window to understand the baryon universe. In this talk, I will give an introduction of our current understanding of the distribution of metal abundances in the universe among different galaxies and within individual galaxies and how they evolve with cosmic time. Interpretations based on empirical models and simulations will also be covered.","Local","","",""]
October[4]=["31","Bartosz Fornal","Utah","Neutron's Dark Secret","Although the neutron was discovered over eighty years ago and has been studied intensively thereafter, it may still be hiding a deep secret. The precise value of the free neutron lifetime is an open question, with two types of experiments (bottle and beam measurements) providing substantially different answers. I will describe the recently proposed interpretation of this discrepancy as a sign of neutron decaying to dark particles. Consistent models for such neutron dark decays can be constructed and they involve either a strongly self-interacting dark sector or a repulsive dark matter-baryon interaction. I will elaborate on the theoretical developments around this idea and describe the efforts undertaken to verify it experimentally.","Local","","",""]
November[0]=["07","Laura Chang","Princeton","Characterizing the Nature of the Galactic Center Excess","The Galactic Center Excess (GCE) of GeV gamma rays can be explained as a signal of annihilating dark matter. Alternatively, some studies have shown that it could be more consistent with emission from unresolved astrophysical point sources, such as millisecond pulsars. Significant effort has been dedicated to determining the origin of the GCE signal, but robustly performing such analyses is fundamentally challenged by the presence of bright, complex astrophysical backgrounds in the Inner Galaxy. In this talk, I will broadly review the current status of the interpretation of the GCE signal. I will present results from recent work on simulated data that takes a pedagogical approach towards understanding and characterizing some of the important challenges in Inner Galaxy point source analyses. I will also discuss findings from ongoing complementary work that seeks to mitigate some of these challenges and perform a more robust point source analysis on real Fermi data.","Yue Zhao","","",""]
November[1]=["14","Noemie Globus","NYU","The origin of the ultra-high energy cosmic-ray dipole","Although their astrophysical sources remain a mystery, new measurements brought by experiments such as the Pierre Auger Observatory and Telescope Array have radically improved our knowledge of the ultra-high energy cosmic-rays (UHECRs), and reported recently a large scale dipole anisotropy.
I will present the UHECR anisotropy expected from large-scale structures with emphasis on the dipole and quadrupole components. I will discuss the sensitivity of these results to the different hadronic interaction models, Galactic and extragalactic magnetic field model parameters.","Dan Wik","","",""]
November[2]=["21","Ke Fang","Stanford","Multi-messenger Astrophysics: Probing Compact Objects with Cosmic Particles","Coordinated detection and interpretation of multiple messenger signals, namely electromagnetic radiation, cosmic rays, neutrinos, and gravitational waves, offer a rewarding way to study compact objects. Successful observations of the neutron star merger event, GW170817, and the potential high-energy neutrino source, blazar TXS 0506+056, marked the opening of the Multi-messenger Era. In this talk, we summarize the current understanding of the four types of messengers. By presenting numerical simulation of particle interaction and propagation in the vicinity of compact objects, we illustrate how high-energy neutrinos and gamma-rays probe non-thermal processes in magnetar-powered transients and in black hole jets. In the second half of the talk, we switch to an observer’s perspective and investigate analysis frameworks aiming to exploit data across wavelengths and messengers. We close the talk by outlooking the future of Multi-messenger Astrophysics, in light of upcoming facilities and new questions brought by recent observations.","Doug Bergman","","",""]
November[3]=["28","","","No Seminar - Thanksgiving Holiday","","","","",""]
December[0]=["05","Aysegul Tumer","Utah","Noncool Core Galaxy Clusters and the Feedback from Their Central Active Galactic Nuclei","The study of the brightest cluster galaxy (BCG) coronae of noncool core (NCC) galaxy clusters and their central active galactic nuclei (AGN) is crucial for understanding the BCG's role on galaxy cluster evolution as well as the activation of the self-regulated cooling and heating mechanism in the central regions of galaxy clusters. In this talk, I would like to present the X-ray properties of the intracluster medium (ICM) of a sample of NCC galaxy clusters and their BCG interstellar medium (ISM), along with their central AGN by using archival XMM-Newton observations.","Local","","",""]
December[1]=["12","","","No Seminar - Final Exams","","","","",""]
December[2]=["19","","","No Seminar - Winter Break","","","","",""]
December[3]=["26","","","No Seminar - Winter Break","","","","",""]
January[0]=["02","","","No Seminar - Winter Break","","","","",""]
January[1]=["09","","","Reserved","","","","",""]
January[2]=["16","","","Reserved","","","","",""]
January[3]=["23","","","Reserved","","","","",""]
January[4]=["30","Evangelos Sfakianakis","Illinois","Multi-Messenger Cosmology: Connecting Inflation to Fundamental Physics","The leading paradigm for the very early universe, responsible for planting the seeds for all structure, is inflation, a period of rapid accelerated expansion. Despite inflation having passed all experimental tests, its relation to string theory and its connection to the rest of cosmic history remain relatively unknown. Recently, surprising new behaviour during inflation has been discovered, altering predictions and possibly helping inflation satisfy certain string theory requirements. I will discuss how we can use current and future experiments, from the Cosmic Microwave background to Gravitational Waves, in order to probe the various processes that occur during inflation and test the content of UV theories, such as String Axions, at very high energies. During inflation, almost the entirety of the energy in the universe is locked into the field that drives inflation. In order for inflation to produce our observable universe, the energy must be transferred to the particles we see around us, like electrons and photons, a process called reheating. Reheating can offer solutions to long standing mysteries, like the matter-antimatter asymmetry in the universe. I will explain how we can use reheating as a particle physics laboratory of immense energy, unreachable with human-made accelerators, and study its connection to late-universe observables, like stochastic Gravitational Waves. This will allow us to peek into the nature of the elusive neutrinos and probe the Higgs particle at very high energies.","Pearl Sandick","JFB 102","",""]
February[0]=["06","","","Reserved","","","","",""]
February[1]=["13","Julian Heeck","UC Irvine","Neutrinos - Harbingers of New Physics","Neutrinos are the most elusive known elementary particles; they fly through all of us in vast numbers but are extremely difficult to detect. Immense progress has been made in analyzing their properties over the last decades, culminating in the surprising discovery of neutrino flavor oscillations. These neutrino oscillations imply that neutrinos have tiny but nonzero masses, which provides strong evidence for physics beyond the Standard Model of particle physics. With the increasing precision in neutrino measurements it has even become possible to use neutrinos as a tool to probe for further new physics, e.g. by studying how neutrinos scatter off electrons and nucleons. In addition, neutrinos could prove uniquely helpful in the search for dark matter and provide complementary information to standard indirect detection signatures.","Pearl Sandick","JFB 102","",""]
February[2]=["18","Gopolang Mohlbeng","BNL","Signals of Dark Matter Beyond the Weak Scale","There is overwhelming astrophysical and cosmological evidence for the existence of dark matter. For decades, particle physicists thought it must be a very well-motivated class of models called weakly interacting massive particles (WIMPs). Though there have been extensive searches for these, a convincing signal remains elusive. We are hence compelled to consider a broader program with novel theoretical ideas and search strategies. In this colloquium, I will give an overview of my work on new scenarios beyond the WIMP paradigm that give striking signals of dark matter, accessible in the near future. I will show that two seemingly disconnected mass scales for dark matter do in-fact complement each other and provide a compelling motivation for accelerator based and underground laboratory searches.","Pearl Sandick","Tuesday JFB 102","",""]
February[3]=["20","Kaori Fuyuto","LANL","The Mystery of the Matter in the Universe","Why do we exist? Most of us must have wondered at least once. Answering it scientifically is one of the most serious and engrossing challenges in modern physics. The question translated into the language of particle physics is: why is there more matter than antimatter in our Universe? Antimatter is composed of antiparticles which have opposite charges to those of their corresponding particles. In the early Universe, both matter and antimatter should have been present in equal amounts. However, looking around the present Universe, everything, such as galaxies, stars, our planet and ourselves, is made solely of matter. This puzzle is known as matter-antimatter asymmetry of the Universe. In this talk, I will discuss theoretical approaches to solving the mystery in terms of particle physics introducing one possible hypothesis, electroweak baryogenesis, which is the most testable scenario in experiments today.","Pearl Sandick","JFB 102","",""]
February[4]=["18","Carsten Rott","SKKU","Exploring the Universe with High Energy Neutrinos","We have arrived at a special moment in time, where we can now observe the Universe in fundamentally new ways using high energy neutrinos, gamma rays, cosmic-rays, and gravitational waves. By viewing the Universe through these cosmic messengers and in their combination an era of discoveries awaits us. This talk will focus on the neutrino frontier and review the tremendous progress that has been achieved over the last few years, including the observation of a diffuse astrophysical neutrino flux by the IceCube Neutrino Observatory and the multi-messenger observation of a flaring blazar coincident with energetic neutrino emissions. Prospects for discovering more extra-terrestrial high-energy neutrino sources including those in our solar system and ways to search for hints of physics beyond the standard model at energy scales beyond the reach of accelerators will be discussed. I will review plans for an upgrade to IceCube and how the detector can be critically enhanced using a novel camera-based calibration system to prepare it for multi-messenger science. The talk will conclude with a vision for the next-generation neutrino observatories and their science cases.","Charlie Jui","Tuesday JFB 102","",""]
February[5]=["27","Zhen Liu","Maryland","Seeking Hidden Sector Physics at Multiple Frontiers","Hidden sectors consisting of particles that do not feel the strong, weak, or electromagnetic gauge forces represent an exciting possibility for physics beyond the standard model. In particular, the particle that makes up the observed dark matter may constitute a fraction of a much larger hidden sector. However, since hidden sectors may couple only very feebly to the standard model, searching for them poses significant challenges. In this colloquium, I present several exciting new ideas in the hunt for hidden sector particles, ranging from small-scale experiments to large-scale experiments, and spanning different frontiers of particle physics. New results from these new search ideas demonstrate their effectiveness. I further discuss the future perspectives in this active research area of dark sector messenger hunting.","Pearl Sandick","JFB 102","",""]
March[0]=["03","Ke Fang","Stanford","Multi-messenger Astrophysics: Probing Compact Objects with Cosmic Particles","The study of compact stellar remnants such as black holes and neutron stars is an important component of modern astrophysics. Recent observations of the first neutron star merger event and an active galactic nucleus as the first candidate high-energy neutrino source open a new way to study compact objects using multi-messengers. The key to coordinated detection and interpretation of multiple messenger signals, namely, electromagnetic radiation, cosmic rays, neutrinos, and gravitational waves, is to understand the link between the messengers. We try to answer this question from both theoretical and observational perspectives. We study ultrahigh-energy cosmic ray propagation in the vicinity of magnetar-powered transients and black hole jets using numerical simulation. We also investigate analysis frameworks aiming to exploit data across multiple wavelengths and messengers. We close the talk by overlooking the future of Multi-messenger Astrophysics, in light of upcoming facilities such as TAx4, SWGO and LSST, as well as new questions brought by recent observations.","Charlie Jui","Tuesday JFB 102","",""]
March[1]=["05","Saveez Saffarian","Utah","A Look Under the Hood of the Coronaviruses","Over the past decade at University of Utah, my lab has investigated the replication mechanism of RNA viruses including HIV and VSV. in this talk, I will present the basic science behind replication mechanism of the coronaviruses, I will highlight similarities between coronaviruses and the viruses we have studied in the lab as well as major differences. The topics will include the general anatomy of the virus, how the virus enters host cells, how it replicates its genome and packages the many progeny virions that are released from each infected cell. I will also highlight how the new imaging modules developed at CCGS can be used to study the coronaviruses and what can we learn by studying the virus at higher resolutions.","Local","CSC 208","",""]
March[2]=["12","","","No Seminar - Spring Break","","","","",""]
March[3]=["19","Amy Furniss","Cal State","CANCELLED","","David Kieda","","",""]
March[4]=["26","Simona Giacintucci","NRL","CANCELLED","","Dan Wik","","",""]
April[0]=["02","Tzu-ching Chang","JPL","CANCELLED","","Zheng Zheng","","",""]
April[1]=["09","Jeremy Tinker","NYU","CANCELLED","","Kyle Dawson","","",""]
April[2]=["17","Mike Lisa","OSU","CANCELLED","","David Kieda","","",""]
April[3]=["23","","","No Seminar - Final Exams","","","","",""]
May[0]=["21","Paul Schechter","MIT","CANCELLED","","Joel Brownstein","","",""]
May[1]=["26","Yana Zhezher","ICRR Tokyo","Highest-energy cosmic rays with the Telescope Array experiment","We will present a series of studies based on the Telescope Array (TA) surface detector data, namely ultra-high-energy cosmic-ray (UHECR) mass composition and composition anisotropy-related analyses and directional UHE gamma-ray searches. Methods based on the applications of machine learning techniques to the multivariate data derived from the TA surface detectors will be discussed. As an example of the implementation of the obtained results, the use of the TA-based directional UHE photon search for constraining the superheavy decaying dark matter will be introduced.","Charlie Jui","5 PM","Zoom",""]
May[2]=["28","Jihyun Kim","Osaka City U","A clue to the origin of ultra-high-energy cosmic rays","An intermediate-scale of anisotropy in the arrival directions of ultra-high-energy cosmic rays (UHECRs) was identified by the Telescope Array (TA) experiment. Those clustered UHECR events, so-called the hotspot, are expected to give us a clue to their origin. However, it remains unanswered because there is no prominent source candidate behind the hotspot. Besides the hotspot, the distribution of TA events on the sky shows another distinctive feature, i.e., a deficit of events toward the Virgo cluster, which has lots of astronomical objects that can be sources of UHECRs. In this talk, I present a model that can account for both characteristic distributions in the identical framework. The magnetized cosmic web structure of the local universe—the Virgo cluster and filaments of galaxies connected to the Virgo cluster—would be responsible for the characteristic distribution of TA events. We find a statistically significant correlation between the TA events and the filaments of galaxies by calculating the statistics for the correlation. Also, we examine the trajectories of UHECRs in the model universes for the further exploration of the suggested model. The feasibility of the model and its astrophysical implications will be discussed.","Charlie Jui","5 PM","Zoom",""]