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(134 results)
First Namesort descendingLast NameTitleAbstract (< 200 words)
IshwareeNeupaneInflation and Cosmology of a FLRW 3-brane with curvature corrections A late epoch cosmic acceleration may be naturally entangled with cosmic coincidence - the observation that at the onset of acceleration the vacuum energy density fraction nearly coincides with the matter density fraction. In this talk I show that this is indeed possible with the cosmology of a Friedmann-Lamaıtre-Robertson-Walker (FLRW) 3-brane in a 5-dimensional anti-de Sitter spacetime. I also present new results that include effects of curvature-squared terms and then argue that Planck results support a simple model of Gauss-Bonnet braneworld cosmology. The effect of a GB coupling is found to be negligibly small at a late epoch, but non-negligible at earlier epochs, including at the epoch of nucleosynthesis. Interestingly, the modified GB braneworld gravity with allows a cosmological bounce, particularly, in the early universe.
GeraintLewisNon-standard Dark Sector CosmologiesAttention is steadily turning towards non-standard dark sector models, where dark matter and dark energy can interact and decay. I will present results from a new suite of simulations of structure evolution in such cosmologies, focusing upon non-linear evolution of galaxies and clusters. These simulations represent a new initiative, under the Survey Simulation Pipeline (SSimPL) to accurately forecast the influence of non-standard dark sectors on observations by new and future facilities.
ChristianeFrigerio MartinsTBA
ChrisPowerTesting Dark Matter with Satellite GalaxiesThe defining prediction of the Cold Dark Matter paradigm is that there is an abundance of small-scale structure in the Universe. On the scale of galaxies, we might expect this small-scale structure to be associated with satellite galaxies. However, the mapping between the small-scale structure and the dark matter hosts of satellites is not straightforward -- it will depend on the physics of galaxy formation, but it will also depend on the nature (i.e. the coldness) of the dark matter. In this talk I will review my recent work on the physics that drives satellite galaxy halo occupancy and on how the properties of satellite galaxies might be used to infer the existence of dark small-scale structure.
IldusNurgalievUniverse is not Dark and is not SingularMissed components in the standard cosmological dynamics are vorticity and shear, kinematic terms. Averaged term of squared vorticity is term of accelerated expansion caused by negative energy of the repulsive factor. Cosmological singularity was a consequence of the unrealistically excessive symmetry of cosmological principle (too detailed symmetry of flow) such as Hubble law. Appropriated realistic one is also linear but has tensor character. Cosmological principle is applied to irregularities – they are homogeneous and isotropic in average. The Big Bang is a reminiscence of the local bounce which is typical among zillions others. Exact solutions are presented. The Big Bang is just local meta-galactic observation of the "Myriads of Bouncing Bangs Model in the eternal Universe.
EmilioElizaldeVacuum fluctuations and non-local gravity modelsWhat drives the acceleration of the Universe expansion? Dark energy, of course, but what is it? Beautiful mathematics, involving the zeta function of pseudodifferential operators, are key in answering this question, crucial to understand the Universe. An alternative is to modify Einstein's gravity, through quantum corrections or otherwise, as in terms of non-local model which seem to exhibit very nice properties.
StefanoBorganiCosmology with galaxy clusters: the role of simulationsI will present results from recent analyses of cosmological hydrodynamic simulations of galaxy clusters, aimed at calibrating clusters as precision cosmological tools. The simulations are carried out using an improved formulation of SPH and include detailed descriptions of a number of astrophysical processes (e.g. star formation, feedback in energy and metals from SN and AGN) that drive galaxy formation and evolution. As such, these simulations provide realistic populations of synthetic clusters that can be used to: (a) calibrate biases in mass measurements from multi-wavelength (X-ray, SZ, optical/near-IR, weak lensing) observations; (b) quantify the impact of baryonic effects on the halo mass function; (c) assessing the robustness of mass proxies. I will discuss the implications of the results in the light of forthcoming and future large surveys of galaxy clusters.
GamalNashed $f(T)$ gravity theories and local Lorentz transformationWe modify the field equations of $f(T)$ gravity theories such that they become invariant under Local Lorentz Transformation (LLT) in the case of spherical symmetry. A ``general tetrad field'', with an arbitrary function of radial coordinate preserving spherical symmetry is provided. We split that tetrad field into two matrices; the first represents a LLT, which contains an arbitrary function, the second matrix represents a proper tetrad field which is a solution to the field equations of $f(T)$ gravitational theory, (which are not invariant under LLT). This ``general tetrad field'' is then applied to the modified field equations of $f(T)$. We show that the effect of the arbitrary function which is involved in the LLT invariably disappears.
AnupamSinghA FIELD THEORY PERSPECTIVE ON DARK ENERGY AND THE GRAVITATIONAL COLLAPSE OF DARK ENERGY FIELD CONFIGURATIONSDark Energy is the dominant component of the total energy density of our Universe. Thus it behooves us to make a careful analysis of it from a fundamental perspective. Since Dark Energy is a low energy phenomenon from the perspective of particle physics and field theory, a fundamental approach based on fields in curved space should be sufficient to address the fundamental properties of field theory. Here we take a field theory approach to Dark Energy. We derive and present the evolution equations for a generic Dark Energy field in curved space-time and then discuss the gravitational collapse for Dark Energy field configurations which leads us to conclude that this will have important and observable cosmological consequences.
ChristofWetterichCrossover from inflation to quintessenceThe approximate scale symmetry for inflation and late dynamical dark energy is related to a crossover between two fixed points. The same scalar cosmon field successfully accounts for dark energy in both epochs within simple three-parameter models of variable gravity. The models can be described equivalently in the big bang or freeze picture. In the latter the evolution is very slow for all epochs and it becomes apparent that the universe is eternal and regular. Tests of the model are early dark energy and the formation of large neutrino lumps.
PyungwonKoDark matter models with local dark gauge symmetriesDM particles are either absolutely stable or very long lived, which can be realized by local or approximate global symmetries. In this talk, I describe a class of dark matter models based on local dark gauge symmetries, either unbroken or broken, weakly or strongly interacting, and discuss the particle identity of the DM particles, the amount of dark radiation, self-interactions of the DM and Higgs phenomenology.
PaoloGondoloTBATBA (I would like to present something on dark matter, perhaps axion dark matter after BICEP2.)
CarlosMunozGravitino dark matter: model and searchesGravitinos are well-known candidates for dark matter (DM) in supersymmetric scenarios. In particular, the R-parity violating “mu from nu” Supersymmetric Standard Model (munuSSM) is an attractive scenario since simply using right-handed neutrinos solves the mu problem of the Minimal Supersymmetric Standard Model while simultaneously explaining the origin of neutrino masses. At the same time, the violation of R-parity renders the gravitino unstable and subject to decay into a photon and a neutrino. This makes it possible to search for gravitino DM with gamma-ray observations. The Fermi Large Area Telescope (Fermi-LAT) collaboration analyses possible monochromatic gamma-ray emission from the Galaxy. As a consequence, the munuSSM gravitino DM parameter space can be strongly constrained.
Jihn E.KimDark energy, dark matter, BICEP2, and trans-Planckian decay constantTo interpret dark energy as a vacuum energy of quintessential axion, we need to consider the QCD axion at the same time. In this set up, one can have an approximate global symmetry which is free of the QCD anomaly. The pseudo-Goldstone boson corresponding to this approximate U(1) is the quintessential axion. The radial field counterpart of the quintessential axion is the inflation which needs a trans-Planckian decay constant. All these issues are described in one framework: discrete symmetries from string.
Ki-YoungChoiThe signatures from dark matter scattering with cosmic raysDark matters around our galaxy can have scatterings with the cosmic rays in our galaxy. If the dark matter has a relatively large couplings, the resultant scattering can induce the gamma rays or neutrino signals with significant flux. I will talk about the signatures and the possibility to detect them in the gamma ray telescopes and neutrino telescopes.
AndrewBeckwithAnalyzing Black Hole super-radiance Emission of Particles/Energy from a Black Hole as a Gedankenexperiment to get bounds on thFROM THE ARTICLE PUBLISHED HERE: Use of super-radiance in BH physics, so dE/dt < 0 specifies conditions for a mass of a graviton being less than or equal to 10^ - 65 grams, and also allows for determing what role additional dimensions may play in removing the datum that massive gravitons lead to 3/4th the bending of light past the planet Mercury.The present document makes a given differentiation between super-radiance in the case of conventional BHs and Braneworld BH super-radiance, which may delineate if Braneworlds contribute to an admissible massive graviton in terms of removing the usual problem of the 3/4th the bending of light past the planet Mercury which is normally associated with massive gravitons. This leads to a fork in the road, between two alternatives with the possibility of needing a multiverse containment of BH structure, or embracing what Hawkings wrote up recently, namely a re do of the Event Horizon hypothesis as we know it.
MikhailKatanaevPoint massive particle in General RelativityIt is well known that the Schwarzschild solution describes the gravitational field outside compact spherically symmetric mass distribution in General Relativity. In particular, it describes the gravitational field outside a point particle. Nevertheless, what is the exact solution of Einstein's equations with \delta-type source corresponding to a point particle is not known. In the present paper, we prove that the Schwarzschild solution in isotropic coordinates is the asymptotically flat static spherically symmetric solution of Einstein's equations with \delta-type energy-momentum tensor corresponding to a point particle. Solution of Einstein's equations is understood in the generalized sense after integration with a test function. Metric components are locally integrable functions for which nonlinear Einstein's equations are mathematically defined. The Schwarzschild solution in isotropic coordinates is locally isometric to the Schwarzschild solution in Schwarzschild coordinates but differs essentially globally. It is topologically trivial neglecting the world line of a point particle. Gravity attraction at large distances is replaced by repulsion at the particle neighborhood.
Eri AtahualpaMena Barbozaspace phase deformation in thermodynamics properties of a black holeMotivated by string theory results we study noncommutative black holes and their thermodynamics properties, we construct a Wheeler deWitt equation and through the Feynmann-Hibbs procedure we can study the noncommutative Hawking's temperature and entropy function of a black hole to make a comparative study with a noncommutative black hole in the Anti deSitter Space. Relations with the noncommutative parameters are also discussed.
RamonMiquelThe Dark Energy Survey: Status and First ResultsThe Dark Energy Survey (DES) is a next-generation large galaxy survey designed to unravel the mystery of the nature of the dark energy that powers the current accelerated expansion of the universe. During the northern fall of 2012 the DES collaboration installed and commissioned DECam, a state-of-the-art 570 mega-pixel optical and near-infrared camera with a large 3 sq. deg. field of view, set at the prime focus of the Víctor M. Blanco 4-meter telescope in CTIO, Chile. A "Science Verification" (SV) period of observations, lasting until late February 2013, followed the DECam commissioning phase, and provided science-quality images for almost 200 sq. deg. at the nominal depth of the survey. The first of five observing seasons then went on from August 2013 to February 2014. At the end of the five seasons, DES will have mapped an entire octant of the southern sky to unprecedented depth, measuring the position on the sky, redshift and shape of almost 300 million galaxies, together with thousands of galaxy clusters and supernovae. With this data set, DES will study the properties of dark energy using four main probes: galaxy clustering on large scales, weak gravitational lensing, galaxy-cluster abundance, and supernova distances. The talk will present the current status of the project, the first scientific results of the survey, based on the SV observations, and the plans and goals for the coming years.
MarcoBruniInteracting vacuum: indications for a late time interaction in the dark sectorMeasurements of anisotropies of the CMB, combined with independent measurements of the cosmic expansion history, such as baryon acoustic oscillations, have provided strong support for the standard model of cosmology, the ΛCDM model. However the latest measurements are in tension with local measurements of the Hubble expansion rate from super- novae Ia and other cosmological observables which point towards a lower growth rate of large-scale structure (LSS), including cluster counts from Sunyaev-Zel’dovich and X-ray observations and redshift-space distortions (RSD) from galaxy peculiar velocities. In this talk I will discuss a minimal generalisation of the ΛCDM model, where vacuum and CDM can interact at late time, showing that this model alleviate this tension.
AdamAmaraModel Breaking and Dark Matter MappingThe talk will open with a new way of designing experiments in cosmology beyond the standard DETF figure-of-merit. This new model breaking approach is designed to use existing data and to look for opportunities for finding deviations from LCDM in any sector of the model. The second half of the talk will focus on the dark matter sector. The focus will be on how mapping of dark matter from large scales (those of the cosmic web) down to the small scales (to dwarf galaxy scales) can be used to combine information from multiple probes to produce a consistent picture of dark matter as measured through its gravitational effects. This, in turn, can be linked with possible particle properties of dark matter. Along with this, I will show some of the latest DES (Dark Energy Survey) results on this topic.
Alexandre RefregierWeak Gravitational Lensing by Large Scale StructureWeak gravitational lensing is a powerful probe of the dark side of the universe. After describing the physical principles of weak lensing, I will review its current observational status. I will then describe current developments in this area and the prospects offered by future wide field survey experiments.
Mei SasakiStatistical properties of dark matter mini-haloes at z ≥ 15Understanding the formation of the first objects in the Universe critically depends on knowing whether the properties of small dark matter structures at high redshift (z ≥ 15) are different from their more massive lower-redshift counterparts. To clarify this point, we performed a high-resolution N-body simulation of a cosmological volume 1 h-1 Mpc comoving on a side, reaching the highest mass resolution to date in this regime. We make precision measurements of various physical properties that characterize dark matter haloes (such as the virial ratio, spin parameter, shape, and formation times, etc.) for the high-redshift (z ≥ 15) dark matter mini-haloes we find in our simulation, and compare them to literature results and a moderate-resolution comparison run within a cube of side-length 100 h-1 Mpc. We find that dark matter haloes at high-redshift have a log-normal distribution of the dimensionless spin parameter centred around bar{λ } ˜ 0.03, similar to their more massive counterparts. They tend to have a small ratio of the length of the shortest axis to the longest axis (sphericity), and are highly prolate. In fact, haloes of given mass that formed recently are the least spherical, have the highest virial ratios, and have the highest spins. Interestingly, the formation times of our mini-haloes depend only very weakly on mass, in contrast to more massive objects. This is expected from the slope of the linear power spectrum of density perturbations at this scale, but despite this difference, dark matter structures at high-redshift share many properties with their much more massive counterparts observed at later times.
Jean-PhilippeUzanDark Energy Review (I'll probably find a better title by then)The influence acceleration of the expansion of the universe have been checked on various observable. After Planck and before Euclidn various scenarios are being refined. I will propose an overview of the theoretical explanations anf the observational landscape.
glennstarkmanThe CMB Anomalies: Still There, Still Anomalous. Why we should careThe Cosmic Microwave Background Radiation is our most important source of information about the early universe. Many of its features are in good agreement with the predictions of the so-called standard model of cosmology -- the Lambda Cold Dark Matter Inflationary Big Bang Theory. However, the large-angle fluctuations of the microwave background exhibit several statistically significant anomalies. On the one hand, if we look at the whole sky the lowest multipoles seem to be correlated both with each other and with the geometry of the solar system. On the other hand, when we look just at the part of the sky that we most trust – the part outside the galactic plane - there is a dramatic lack of large angle correlations. So much so that it challenges basic predictions of the standard model. We discuss these anomalies and how we might test whether they reflect profound underlying physics, or just statistical flukes.
MuhammadSharifInflationary Universe Model We study the warm inflation using vector fields in the background of locally rotationally symmetric Bianchi type I universe model. We explore slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) under slow-roll approximation. The observational parameter of interest, i.e., tensor-scalar ratio in terms of inflaton is also discussed.
CamilleBonvinRelativistic effects in Large Scale Structure Surveys
GustavoYepesMocking the Universe: Large Volume Simulations for Galaxy Redshift SurveysLarge volume N-body simulations are becoming an indispensable tools for present day (eg. BOSS, DES) and upcoming (DESI, J-PAS, 4MOST, LSST, Euclid) galaxy redshift survey experiments that aim at measuring the evolution of the expansion factor of the Universe through standard rulers like the Baryonic Accoustic Oscillations scale in the galaxy clustering. These N.body simulations require two main ingredients: large volumes to reproduce the survey geometry and enough mass resolution to resolve all halos that are hosting the same galaxies than observed in the different experiments. They can then be used to account for the non-linearites due to gravitational evolution in the halo clustering with respect to the dark matter one at the BAO scale, as well as to produce realistic mock catalogs that can be used to estimate the errors in the different statistics used to measure the galaxy clustering properties. In this talk I will report the latest results from two large volume simulation efforts in which I am actively participating: The JUBILEE and MULTIDARK simulations projects.
CelineBoehmDark Matter interactions
YunguiGongThe modified Lyth boundTo reconcile the BICEP2 measurement on the tensor-to-scalar ratio $r$ with {\em Planck} constraint, a large negative running of the scalar spectral index $n_s$ is needed. So the inflationary observable such as $n_s$ should be expanded at least to the second-order slow-roll parameters for single field inflationary models. The large value of $r$ and Lyth bound indicate that it is impossible to obtain the sub-Planckian excursion for the inflaton. Considering a fifth-order polynomial potential for inflation, we show that it not only agrees with both the BICEP2 and Planck results, but also violates the Lyth bound. Thus, we propose an absolutely minimal bound $\Delta\phi/M_{\rm Pl}>\sqrt{r/8}$ on the inflaton excursion for single field inflation, which can be applied to the non-slow-roll inflation as well. This bound excludes the possibility of the small field inflation with $\Delta\phi<0.1 M_{\rm Pl}$ if the BICEP2 result on $r$ stands.
FabioIoccoDark Matter in the Milky Way: an unbiased determination.We use a new compilation of data for the Rotation Curve of our own Galaxy in order to assess evidence for a dark component of matter. We construct the rotation curve expected from a large sample of models of the baryonic (star and gas) component of the Milky Way, and infer the missing component with high statistical evidence. This model-independent approach shows evidence for a dark component without any explicit dependence neither on the shape of the DM profile, nor on the properties of stellar population dynamics, typically affecting this sort of analysis.
LandmanBesterWhat's inside the cone?The problem of reconstructing the background cosmological metric directly from observations is known as the inverse problem in cosmology. This talk will be about the inverse problem in spherically symmetric dust universes that may include a cosmological constant. I will show how Gaussian process regression can be used to smooth data on the current past lightcone so that it can be used as input to a numerical integration scheme that solves the Einstein field equations in observational coordinates.
StefanGottloeberNear field cosmology with constrained simulations: the CLUES projectCosmological simulations are the driving force behind much of our understanding of the formation of structure in the universe. Such simulations must cover a representative volume of the universe, but this request comes at the expense of the mass and force resolution. Using the observed positions and radial velocities of nearby galaxies as constraints imposed on the initial conditions of the simulations the resulting constrained simulations successfully reproduce the observed structures in the nearby universe. Zoomed high resolution gasdynamical simulations allow to study the formation of the Local Group with the Milky Way and Andromeda in the right large scale environment of the cosmic web. We perform such simulations within the CLUES project (Constrained Local UniversE simulations - using the new observational data of CosmicFlows2. I am going to discuss new approaches to improve the simulations and will review recent results based on our constrained simulations.
GeoffBeckEvolution of Dark Matter Halo Radio EmmissionsDark matter remains a major gap in the understanding of modern physics with many proposed routes to direct and indirect detection. In this study we model the radio emission from neutralino annihilation in DM halos assuming various annihilation channels, a model of the magnetic field and an exploration of a range of redshifts. Using this model we provide estimates for the detectability of neutralino annihilation radio signatures via the SKA and derive upper bounds on the annihilation cross-section in the event of non-detection. We find that the strongest constraints arise from large objects, galaxies and clusters, which could be detectable out to redshift of order 1 and provides more stringent constraints than the relic abundance in the event of non-detection. Additionally we demonstrate that differing annihilation channels have distinct spectral signatures in the resulting radio emissions that could be observable with the future SKA.
AvaniPatelCurvature Singularities in Modified Theories of GravityIn this talk, I will be discussing the problem of Curvature Singularity which arises in f(R) theories. The f(R) Theory is a modification of gravitational theory compared to Einstein’s General Relativity. In these theories, we try to modify gravitational lagrangian by adding higher order curvature corrections without spoiling successes of GR. But, any modified gravity theory must satisfy some validity criteria to be theoretically consistent. Curvature Singularity is common problem most f(R) Theories encounter with. It is a coordinate free singularity in which curvature diverges to infinity in a finite time. I will be discussing about two different methods to find the presence of singularity and their limitations. I will also take extended Hu-Sawicki model as an example and discuss curvature singularity problem and local gravity constraint in it.
Wimde BoerA novel, multi-wave length investigation of the gamma-ray sky using FERMI, PLANCK and ROSAT dataThe 5-years data from the Fermi satellite provide a detailed map of the diffuse gamma-ray sky, which is of great interest for indirect dark matter searches. The main contributions for diffuse gamma-rays are well known and these processes have all been studied in the laboratory, so the spectral shapes of the gamma-ray contributions are known. These known energy spectra can be used as templates in a fit to the Fermi data, which yields the normalization, and hence the fluxes, for the various contributions. After optimizing the CR spectra, which are taken to be the same for all sky directions, there is still a missing hard component in the gamma-ray spectra towards the Galactic centre, which can be ascribed to the Fermi bubbles. From the template fits we find that the bubbles arise not only from the Galactic centre, but also from the Galactic bar and spiral arms. The underlying proton spectrum for the bubble template is found to be the hard 1/E^2 spectrum, expected for freshly-accelerated protons in supernova remnants. Details can be found in e-Print: arXiv:1407.4114. Comparison of the multi-GeV Fermi Bubbles with the microwave Planck Haze and the X-ray sky-map of ROSAT will be made. After understanding the background towards the Galactic centre much better one can search for dark matter signatures in the gamma-ray sky. First results will be given. Comments on recent claims for evidence for a 30 GeV WIMP from the Fermi data (arXiv:1402.6703) will be commented upon.
HristuCuletu On the Morris - Thorne wormhole The properties of a particular Misner - Thorne wormhole are investigated. The ''exotic stress energy'' needed to maintain the wormhole open corresponds to a massless scalar field whose Lagrangean density contains a negative kinetic term. While the Komar energy of the spacetime is vanishing due to the negative energy density and radial pressure, the ADM energy is (minus) the Planck energy. The timelike geodesics are hyperbolae and any static observer is inertial. The null radial trajectories are also hyperbolae and Lorentz invariant as Coleman- de Luccia expanding bubble or Ipser-Sikivie domain wall. Using a different equation of state for the fluid on the dynamic wormhole throat of Redmount and Suen, we reached an equation of motion for the throat (a hyperbola) that leads to a negative surface energy density and the throat expands with the same acceleration $2\pi |\sigma|$ as the Ipser-Sikivie domain wall.
AnnaLamperstorferConstraining box-shaped gamma-ray features with CTAA sharp spectral feature in the gamma-ray sky would be a "smoking gun" for dark matter annihilations. In this work we focus on box-shaped gamma-ray spectral features, that can arise in models where the dark matter annihilates into intermediate scalars that then decay into a pair of photons. This kind of signal can be severely constrained by the future Cherenkov Telescope Array. Using detailed information on the instrument such as the effective area and the energy resolution, we derive projected limits on box-shaped gamma-ray features for heavy dark matter particles, a mass range that is not accessible by any other detection method. Our region of interest is a 2° x 2° region around the Galactic Center, a prime target for dark matter annihilations due to its large dark matter density. The robustness of our approach is tested by varying the size and location of the energy windows within the sliding energy window technique for narrow and wide boxes. We conclude by discussing the relevance of our constraints for particular particle physics models featuring gamma-ray boxes.