Browsing by Subject "OLIVEFEST"
Now showing 1 - 20 of 34
- Results Per Page
- Sort Options
Item Alpha-attractors and B-mode targets(2017-05) Kallosh, RenataWe discuss alpha-attractor cosmological models which can be derived by a consistent reduction from theories with maximal supersymmetry, like M-theory, superstring theory, or maximal supergravity, to minimal supersymmetry models. These models provide a set of targets for the future detectors of primordial gravitational waves, scanning the region of tensor to scalar ratio between 1/100 and 1/1000.Item Antimatter cosmic rays: recent results with the semi-analytic approach(2017-05) Salati, PierreThe nature of dark matter, an essential component of the Universe, is still unresolved. The best candidate is a weakly interacting particle yet to be discovered at accelerators. In most models, these exotic species annihilate and yield in particular antiprotons and positrons, hence the connection between the dark matter problem and antimatter cosmic rays. Distortions and anomalies in the antiproton and positron spectra are actively searched. A positron excess has actually been discovered and recently confirmed. But claiming that dark matter species have been discovered in the cosmic radiation requires to understand it and to properly model the various backgrounds in which the signal might be found. To achieve this goal, a key ingredient is the transport of charged particles within the magnetic halo of the Milky Way. In this talk, I will focus on a few (semi)-analytic methods used to solve the transport of cosmic rays and derive their fluxes at the Earth. I will then describe the so-called pinching method, which allows for a fast and reliable calculation of the positron spectrum even at low energies. Finally, with the help of this new tool, I will reinvestigate if dark matter can source the positron excess and I will set limits on MeV dark matter candidatesItem Astrophysical Searches for Dark Matter: A Status Report(2017-05) Profumo, StefanoI will give an update on current status and future prospects in searching for the particle nature of dark matter with astronomical and cosmic ray observations. I will discuss a few more or less controversial signals, and how they can be tested and probed.Item Banquet Presentation(2017-05) Ellis, JohnItem Baryogenesis from Dark Sector(2017-05) Kainulainen, KimmoThe measured Higgs mass value 125 GeV may suggest that standard model (SM) may be UV-complete up to Planck scale. Yet, questions of the nature of the dark matter and of the origin of baryons remain unsolved in the SM. The latter is particularily difficult to address in UV-complete low energy extensions of SM. The main problem is finding enough CP-violation consistent with existing laboratory bounds. I will show that a simple UV-complete model, with a fermionic dark matter particle X coupling to a new singlet scalar S can realize successful electroweak baryogenesis. In our model X gets a CP asymmetry that is transferred to the standard model through a CP portal interaction, coupling X to tau leptons and an inert Higgs doublet. The CP asymmetry induced in left-handed tau leptons biases sphalerons to produce the baryon asymmetry. The model has promising discovery potential at the LHC, while robustly providing a large enough baryon asymmetry and correct dark matter relic density with reasonable values of the couplings.Item A Bitter Pill? The Primordial Lithium Problem(2017-05) Fields, BrianBig-bang nucleosynthesis (BBN) describes the production of the lightest elements during the first three minutes of cosmic time, and represents our earliest reliable probe of the universe. BBN has stood as both cornerstone of modern cosmology and particle astrophysics, and Keith Olive has made fundamental contributions to BBN over a span of four decades. I will review BBN and Keith's hand in it, emphasizing the transformative influence of cosmic microwave background experiments in precisely determining the cosmic baryon density. Standard BBN combines this with the Standard Model of particle physics to make tight predictions for the primordial light element abundances. Deuterium observations match these predictions spectacularly, helium observations are in good agreement, but lithium observations (in metal-poor halo stars) are significantly discrepant-–this is the ”lithium problem.” Over the past decade, the lithium discrepancy has become more severe, and very recently the solution space has shrunk dramatically, with all resolutions of the problem facing stringent constraints. Future observations will either confirm surprises in stellar astrophysics, or most intriguingly, could reveal new physics at play in the early universe.Item Bringing Astrophysics and Cosmology to the Particle Data Book(2017-05) Barnett, MichaelFor 32 years, the outstanding work of Keith Olive has brought astrophysics and cosmology (A&C) to our community through his major contributions to the Particle Data Book. He has brought A&C to the Data Listings as well as to the eight Review articles. PDG is a large collaboration of 223 authors from 148 institutions in 24 countries. During the Olive era, citations grew enormously. For the last edition, downloads of the A&C reviews totaled 137,000.Item Constraints on superstrings, inflation, and extra dimensions from the CMB and big bang nucleosynthesis(2017-05) Mathews, GrantThe energy scale of superstrings was obtainable iduring the early moments of chaotic inflation out of the string theory landscape. This talk explores the possibility that a specific superstring excitation may have made itself known via its coupling to the field of inflation. This may have left an imprint of “dips” in the power spectrum of temperature fluctuations in the cosmic microwave background. The identification of this particle as a superstring is possible because there may be evidence for different oscillator states of the same superstring that appear on different scales on the sky. It will be shown that from this imprint one can deduce the mass, number of oscillations, and coupling constant for the superstring. Although the evidence is marginal, this may constitute the first observation of a superstring in Nature. At the same time, the existence of extra dimensions during inflation impacts the tensor to scalar ratio and the running spectral index. We summarize how the constraints on inflation shift when embedded in higher dimensions. Finally, higher dimensions also impact the cosmic expansion through the projection of curvature from the higher dimension in the “dark radiation” term. We summarize current constraints from BBN and the CMB on this brane-world dark radiation term.Item Dark Matter Candidates in a Heavy QCD Axion Model(2017-05) Ibe, MasahiroItem Dark Matter: a Historical Perspective(2017-05) Srednicki, MarkI will review the impact of the dark matter problem on particle physics, and summarize where we stand today.Item Dark Stars: Dark Matter Annihilation can power the first stars(2017-05) Freese, KatherineThe first phase of stellar evolution in the history of the Universe may be Dark Stars (DS), powered by dark matter heating rather than by nuclear fusion. Weakly Interacting Massive Particles, which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel, with lifetimes from millions to billions of years. Dark stars are very bright diffuse puffy objects during the DS phase, and grow to be very massive. In fact, we have found they can to grow to 10^5-10^7 solar masses with luminosities 10^9-10^11 solar luminosities. Such objects will be observable with James Webb Space Telescope (the sequel to HST). Once the dark matter fuel is exhausted, the DS becomes a heavy main sequence star; these stars eventually collapse to form massive black holes that may provide seeds for supermassive black holes observed at early times as well as in galaxies today.Item From local chemical evolution to cosmic chemical evolution(2017-05) Vangioni, ElisabethMy scientific life with Keith began about twenty five years ago with the study of the chemical evolution of light elements :cosmological elements D, He3, He4 and Li7 and spallative elements, LiBeB. Recently, major CMB results coming from WMAP and Planck, and observations of the total luminosity density leading to significant progress in establishing the star formation rate (SFR) at high redshift, led us to study in detail primordial stars say, Pop III stars, and their different properties (mass and associated nucleosynthesis, related ionizing power..), all that in a cosmological context. Presently, I will present the global cosmic chemical evolution within the framework of hierarchical formation of structures, in a merger tree context, to have a look at the early universe: reionization of the Universe, gamma ray burst and correlation with high z SFR, metal dispersion in DLAs... Finally, the discovery of gravitational waves coming from binary black holes mergers opens a new astrophysical window and we can, thanks to our nucleosynthetic approach, give some constraints on the cosmic binary compact object merger rates and associated stochastic gravitational backgroundItem A galaxy and it's dark matter profile: a story of enhanced annihilations(2017-05) Sandick, PearlIn this talk I’ll discuss a scenario in which a spike in the dark matter density profile in the subparsec region around the supermassive black hole at the center of the Milky Way galaxy gives rise to enhanced dark matter annihilations and, consequently, to enhanced gamma-ray emissions. Bounds on these emissions can be used to constrain dark matter models. In particular, I’ll discuss the importance of modeling the spike’s history for these endeavors. Gravitational interactions of the spike with baryons can lead to the depletion of the spike radius over time, and the limits one obtains on the properties of dark matter vary profoundly depending on the depletion. I will discuss these issues in the context of generic particle physics models that allow for velocity-dependent dark matter annihilation cross sections, and also to a class of simplified dark matter models with t-channel mediators. Finally, if the properties of dark matter are known, one can place constraints on the form of the dark matter spike. I’ll present the constraints on the form of the spike under the assumption that the gamma-ray emission from the extended Galactic Center region observed by Fermi is due to dark matter annihilations.Item Gravitation: constants, a wall and some waves(2017-05) Uzan, Jean-PhilippeOver the past 10 years, I had the chance to hide behind the wall of fundamental constants with Keith, trying to surprise their idle variation. Not catch I may say but it allowed our French-American team to investigate various extensions of general relativity and to test the equivalence principle during big-bang nucleosynthesis and in population III stars. Recently, we dived in the gravity wave background, opening new directions of research on gravity and astrophysics.Item Gravitino Dark Matter(2017-05) Spanos, VassilisWe will discuss issues on gravitino dark matter models, especially after the resent experimental results from the LHC and from experiments that are looking for dark matter either directly or indirectly. After reviewing details of this scenario, we will examine possible future research directions.Item Keith Inflated(2017-05) Nanopoulos, DimitriA Flipped Model for “Everything” below The Planck scale is presented.It is based on No-Scale Supergravity x Flipped SU(5),both components derivable,in principle,from string theory and providing: A SU(N,1) No-Scale Inflation ,avatarized as a Starobinsky -like model ,but with distinctive differences and automatically embedded in Flipped SU(5),specific Cosmological history of the Universe that leads to Supercosmology, strong reheating,controlled entropy release,baryon asymmetry ,on the nose,through RH heavy neutrinos,neutrino masses/ mixings,in accordance with present data and stable enough protons,but reachable ,in near future,lifetime,and a LHC attainable SUSY spectrum. Appropriately enough, Keith has played a pivotal role on all the above ,who sounds like the end (???) result of 35 years group work...Item Keith’s dark side (and some others)(2017-05) Ellis, JohnAfter some historical and personal reminiscences, I will discuss what we can learn about the possible scale of supersymmetry from the density of dark matter, and the prospects for discovering supersymmetry at the LHC, in direct searches for dark matter scattering and in experiments at future colliders.Item Large field inflation: Recent progress and observational predictions(2017-05) Linde, AndreiI will describe the new generation of inflationary models with plateau potentials and their observational predictions. I will also discuss the problem of initial conditions for inflation in such models.Item Light particle solutions to the cosmological lithium problem(2017-05) Pospelov, MaximItem the limits of cosmology(2017-05) Silk, JosephOne of our greatest challenges in cosmology is understanding the origin of the structure of the universe, and in particular the formation of the galaxies. I will describe how the fossil radiation from the beginning of the universe, the cosmic microwave background, has provided a window for probing the initial conditions from which structure evolved and seeded the formation of the galaxies. I will review the outstanding cosmological issues that remain to be resolved, and suggest an optimal choice of future strategy in order to make further progress on understanding our cosmic origins.