- Light-time correction

by Manoj Agravat09 Mar 2015 17:26 - Electroweak physics

by Dr. Emmanuel Lipmanov27 Jan 2015 18:53 - Poisson distribution

by Mahdi Ranjbar Zefreh20 Dec 2014 20:47 - Thermalisation

by Mahdi Ranjbar Zefreh18 Dec 2014 14:11 - Quadrature

by Nicolas Guarin Zapata11 Oct 2014 01:22 - Wigner transform

by Dr. Claude Becker06 Apr 2011 14:04 - Dzyaloshinskii-Moriya interaction

by Dr. George Jackeli28 Aug 2009 09:41 - RKKY interaction

by Dr. Vadim Cheianov31 Aug 2009 09:28 - Minimal Dark Matter

by Dr. Marco Cirelli05 Dec 2010 22:13 - Kaluza-Klein dark matter

by Dr. Geraldine Servant05 Dec 2010 22:13

- We study the existence of ground states for the coupled Schr\"odinger system \begin{equation} \left\{\begin{array}{lll} \displaystyle -\Delta u_i+\lambda_i u_i= \mu_i |u_i|^{2q-2}u_i+\sum_{j\neq i}b_{ij} |u_j|^q|u_i|^{q-2}u_i \\ u_i\in H^1(\mathbb{R}^n), \quad i=1,\ldots, d, \end{array}\right. \end{equation} $n\geq 1$, for $\lambda_i,\mu_i >0$, $b_{ij}=b_{ji}>0$ (the so-called "symmetric attractive case") and $1<q<n/(n-2)^+$. We prove the existence of a nonnegative ground state $(u_1^*,\ldots,u_d^*)$ with $u_i^*$ radially decreasing. Moreover we show that, for $1<q<2$, such ground states are positive in all dimensions and for all values of the parameters.Nehari manifoldMultidimensional ArrayNonnegativeCauchy-Schwarz inequalityManifoldMaximum principleCritical pointMaiaNonlinear opticsEnergy level...
- We study collective excitations in systems described by chiral kinetic theory in external magnetic field. We consider high-temperature weak-coupling plasma, as well as high-density Landau Fermi liquid with interaction not restricted to be weak. We show that chiral magnetic wave (CMW) emerges in hydrodynamic regime (at frequencies smaller than collision relaxation rate) and the CMW velocity is determined by thermodynamic properties only. We find that in a plasma of opposite chiralities, at frequencies smaller than the chirality-flipping rate, the CMW excitation turns into a vector-like diffusion mode. In the interacting Fermi liquid, the CMW turns into the Landau zero sound mode in the high-frequency collisionless regime.Relaxation Time ApproximationKinetic equationWeyl fermionChiral fermionRelaxation timeAntiparticleSphaleronChiral anomalyZero modeBerry phase...
- This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (Search for Hidden Particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, $\tau\to 3\mu$ and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the Standard Model and describe interactions between new particles and four different portals - scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the Standard Model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflationSHiP experimentBeyond the Standard ModelWeak interactionDark matter candidateProton beamSuper Proton SynchrotronAxion-like particleNeutrino massTau neutrinoSupersymmetry...
- Memes are the cultural equivalent of genes that spread across human culture by means of imitation. What makes a meme and what distinguishes it from other forms of information, however, is still poorly understood. Our analysis of memes in the scientific literature reveals that they are governed by a surprisingly simple relationship between frequency of occurrence and the degree to which they propagate along the citation graph. We propose a simple formalization of this pattern and we validate it with data from close to 50 million publication records from the Web of Science, PubMed Central, and the American Physical Society. Evaluations relying on human annotators, citation network randomizations, and comparisons with several alternative approaches confirm that our formula is accurate and effective, without a dependence on linguistic or ontological knowledge and without the application of arbitrary thresholds or filters.Cluster of nodesStatisticsRankingSubcategoryComplex systemsCitation networkCitation graphKeyphraseGeneHuman dynamics...
- We develop the generalized Cartan Calculus for the groups $G=$SL$(2,\mathbb{R})\times\mathbb{R}^+$, SL$(5,\mathbb{R})$ and SO(5,5). They are the underlying algebraic structures of $d=9,7,6$ exceptional field theory, respectively. These algebraic identities are needed for the "tensor hierarchy" structure in exceptional field theory. The validity of Poincar\'e lemmas in this new differential geometry is also discussed. Finally we explore some possible extension of the generalized Cartan calculus beyond the exceptional series.Gauge fieldCovarianceLie derivativeM-theoryChain complexDifferential form of degree threeTwo-formSymmetry groupIsomorphismExterior dimension...
- We analyze the high-energy neutrino events observed by IceCube, aiming to probe the initial flavor of cosmic neutrinos. We study the track-to-shower ratio of the subset with energy above 60 TeV, where the signal is expected to dominate and show that different production mechanisms give rise to different predictions even accounting for the uncertainties due to neutrino oscillations. We include for the first time the passing muons observed by IceCube in the analysis. They corroborate the hypotheses that cosmic neutrinos have been seen and their flavor matches expectations.MuonEarthEffective areaNeutrino flavorNeutrino productionWeak neutral current interactionAtmospheric neutrinoMuon neutrinoNormal hierarchyLikelihood function...
- Supernova remnants are likely to be the accelerators of the galactic cosmic rays. Assuming the correctness of this hypothesis, we develop a method to extract the parent cosmic ray spectrum from the VHE gamma ray flux emitted by supernova remnants (and other gamma transparent sources). Namely, we calculate semi-analytically the (inverse) operator which relates an arbitrary gamma ray flux to the parent cosmic ray spectrum, without relying on any theoretical assumption about the shape of the cosmic ray and/or photon spectrum. We illustrate the use of this technique by applying it to the young SNR RX J1713.7-3946 which has been observed by H.E.S.S. experiment during the last three years. Specific implementations of the method permit to use as an input either the parameterized VHE gamma ray flux or directly the raw data. The possibility to detect features in the cosmic rays spectrum and the error in the determination of the parent cosmic ray spectrum are also discussed.Cosmic raySupernova remnantCosmic ray spectrumHadronizationCosmic ray fluxRX J1713.7-3946Observational errorVery high energy gamma-rayFine structurePrimary proton spectrum...
- A large fraction of SN1987A electron antineutrino events has been recorded in the first second. We study how this observation fits into the conventional paradigm for neutrino emission, and show that there is a 3.2 sigma hint for an initial accretion phase. This phase involves a large fraction of the energy emitted in neutrinos and antineutrinos, about 20 % or larger. The occurrence of neutrino oscillations strengthens these inferences. We discuss why three flavor oscillations with normal mass hierarchy are completely acceptable, whereas oscillations with inverted mass hierarchy require more troublesome interpretations, if theta(13) is above 0.5-1 degrees.AccretionNeutrinoSupernova 1987AAntineutrinoElectron antineutrinoNeutrino oscillationsInverted hierarchyNormal hierarchyPositronStatistics...
- Ultra-deep observations of ECDF-S with Chandra and XMM-Newton enable a search for extended X-ray emission down to an unprecedented flux of $2\times10^{-16}$ ergs s$^{-1}$ cm$^{-2}$. We present the search for the extended emission on spatial scales of 32$^{\prime\prime}$ in both Chandra and XMM data, covering 0.3 square degrees and model the extended emission on scales of arcminutes. We present a catalog of 46 spectroscopically identified groups, reaching a redshift of 1.6. We show that the statistical properties of ECDF-S, such as logN-logS and X-ray luminosity function are broadly consistent with LCDM, with the exception that dn/dz/d$\Omega$ test reveals that a redshift range of $0.2<z<0.5$ in ECDF-S is sparsely populated. The lack of nearby structure, however, makes studies of high-redshift groups particularly easier both in X-rays and lensing, due to a lower level of clustered foreground. We present one and two point statistics of the galaxy groups as well as weak-lensing analysis to show that the detected low-luminosity systems are indeed low-mass systems. We verify the applicability of the scaling relations between the X-ray luminosity and the total mass of the group, derived for the COSMOS survey to lower masses and higher redshifts probed by ECDF-S by means of stacked weak lensing and clustering analysis, constraining any possible departures to be within 30% in mass. Abridged.Point sourceGalaxyDiffuse sourcePoint spread functionChandra Deep Field South surveyX-ray luminosity functionLuminosityCalibrationCosmologyCOSMOS survey...
- The energy spectrum of the cosmic microwave background (CMB) allows constraining episodes of energy release in the early Universe. In this paper we revisit and refine the computations of the cosmological thermalization problem. For this purpose a new code, called CosmoTherm, was developed that allows solving the coupled photon-electron Boltzmann equation in the expanding, isotropic Universe for small spectral distortion in the CMB. We explicitly compute the shape of the spectral distortions caused by energy release due to (i) annihilating dark matter; (ii) decaying relict particles; (iii) dissipation of acoustic waves; and (iv) quasi-instantaneous heating. We also demonstrate that (v) the continuous interaction of CMB photons with adiabatically cooling non-relativistic electrons and baryons causes a negative mu-type CMB spectral distortion of DI_nu/I_nu ~ 10^{-8} in the GHz spectral band. We solve the thermalization problem including improved approximations for the double Compton and Bremsstrahlung emissivities, as well as the latest treatment of the cosmological recombination process. At redshifts z <~ 10^3 the matter starts to cool significantly below the temperature of the CMB so that at very low frequencies free-free absorption alters the shape of primordial distortions significantly. In addition, the cooling electrons down-scatter CMB photons introducing a small late negative y-type distortion at high frequencies. We also discuss our results in the light of the recently proposed CMB experiment Pixie, for which CosmoTherm should allow detailed forecasting. Our current computations show that for energy injection because of (ii) and (iv) Pixie should allow to improve existing limits, while the CMB distortions caused by the other processes seem to remain unobservable with the currently proposed sensitivities and spectral bands of Pixie.Electron temperatureCompton scatteringCMB temperatureEffective temperatureRelic particlesIonizationExpansion of the UniverseEvolution equationPartial differential equationSoft photons...
- We present VLT-UVES Li abundances for 28 halo dwarf stars between [Fe/H]=-2.5 and -3.5, 10 of which have [Fe/H]<-3. Four different T_eff scales have been used. Direct Infrared Flux Method (IRFM) has been used on the basis of 2MASS infrared photometry. H_alpha wings have been fitted against synthetic grids computed by means of 1D LTE atmosphere models, assuming different self-broadening theories. Finally, a grid of H_alpha profiles has been computed by means of 3D hydrodynamical atmosphere models. The Li I doublet at 670.8 nm has been used to measure A(Li) by means of 3D hydrodynamical NLTE spectral syntheses. An analytical fit of A(Li)(3D, NLTE) as a function of equivalent width, T_eff, log g, and [Fe/H] has been derived and is made available. A(Li) does not exhibit a plateau below [Fe/H]=-3. A strong positive correlation with [Fe/H] appears, not influenced by the choice of the T_eff estimator. From a linear fit, we obtain a strong slope of about 0.30 dex in A(Li) per dex in [Fe/H], significant to 2-3 sigma, and consistent among all the four T_eff estimators. A significant slope is also detected in the A(Li)--T_eff plane, driven mainly by the coolest stars in the sample which appear Li-poor. Removing such stars does not alter the behavior in the A(Li)-[Fe/H] plane. The scatter in A(Li) increases by a factor of 2 towards lower metallicities, while the plateau appears very thin above [Fe/H]=-2.8. The meltdown of the Spite plateau below [Fe/H]\sim-3 is established, but its cause is unclear. If the primordial A(Li) is the one derived from WMAP, it appears difficult to envision a single depletion phenomenon producing a thin, metallicity independent plateau above [Fe/H]=-2.8, and a highly scattered, metallicity dependent distribution below. The fact that no star below [Fe/H]=-3 lies above the plateau suggests that they formed at plateau level and underwent subsequent depletion.AbundanceBig bang nucleosynthesisStellar atmosphereEffective temperatureCalibrationReddeningStatisticsNear-infraredMetal-poor starPhotosphere...
- We present the results of a new, non-parametric method to reconstruct the Galactic dark matter profile directly from observations. Using the latest kinematic data to track the total gravitational potential and the observed distribution of stars and gas to set the baryonic component, we infer the dark matter contribution to the circular velocity across the Galaxy. The radial derivative of this dynamical contribution is then estimated to extract the dark matter profile. The innovative feature of our approach is that it makes no assumption on the functional form nor shape of the profile, thus allowing for a clean determination with no theoretical bias. We illustrate the power of the method by constraining the spherical dark matter profile between 2.5 and 25 kpc away from the Galactic centre. The results show that the proposed method, free of widely used assumptions, can already be applied to pinpoint the dark matter distribution in the Milky Way with competitive accuracy, and paves the way for future developments.Rotation CurveMilky WayInner galaxyNumerical simulationSolar neighborhoodQuadratureStatistical errorSystematic errorDark Matter Density ProfileCosmology...
- The first observation of the $B^0_s\to\eta'\eta'$ decay is reported. The study is based on a sample of proton-proton collisions corresponding to $3.0$ ${\rm fb^{-1}}$ of integrated luminosity collected with the LHCb detector. The significance of the signal is $6.4$ standard deviations. The branching fraction is measured to be $[3.31 \pm 0.64\,{\rm (stat)} \pm 0.28\,{\rm (syst)} \pm 0.12\,{\rm (norm)}]\times10^{-5}$, where the third uncertainty comes from the $B^{\pm}\to\eta' K^{\pm}$ branching fraction that is used as a normalisation. In addition, the charge asymmetries of $B^{\pm}\to\eta' K^{\pm}$ and $B^{\pm}\to\phi K^{\pm}$, which are control channels, are measured to be $(-0.2 \pm1.3)\%$ and $(+1.7\pm1.3)\%$, respectively. All results are consistent with theoretical expectations.Systematic errorHadronizationInvariant massStandard ModelStatisticsMass distributionKaonQuarkCalibrationStatistical error...
- Relativistic jets are one of the most powerful manifestations of the release of energy related to the supermassive black holes at the centre of active galactic nuclei (AGN). Their emission is observed across the entire electromagnetic spectrum, from the radio band to gamma rays. Despite decades of efforts, many aspects of the physics of relativistic jets remain elusive. In particular, the location and the mechanisms responsible for the high-energy emission and the connection of the variability at different wavelengths are among the greatest challenges in the study of AGN. Recent high resolution radio observations of flaring objects locate the high-energy emitting region downstream the jet at parsec scale distance from the central engine, posing questions on the nature of the seed photons upscattered to gamma-rays. Furthermore, monitoring campaigns of the most active blazars indicate that not all the high energy flares have the same characteristics in the various energy bands, even from the same source, making the interpretation of the mechanism responsible for the high-energy emission not trivial. Although the variability of the most luminous blazars is well explained by the "shock-in-jet" scenario, the sub-class of TeV emitting objects suggests a more complex emission model with velocity gradients in a structured jet. This contribution presents results obtained by recent multiwavelength campaigns of blazars aimed at studying the radio and gamma-ray connection and the physical mechanisms at the basis of the emission in these low and high energy bands.Light curveVery long baseline interferometryEGRETFlat spectrum radio quasarBroad-line regionRadio galaxyTime delayLimb brighteningBL LacertaeSynchrotron...
- Large scale models of physical phenomena demand the development of new statistical and computational tools in order to be effective. Many such models are `sloppy', i.e., exhibit behavior controlled by a relatively small number of parameter combinations. We review an information theoretic framework for analyzing sloppy models. This formalism is based on the Fisher Information Matrix, which we interpret as a Riemannian metric on a parameterized space of models. Distance in this space is a measure of how distinguishable two models are based on their predictions. Sloppy model manifolds are bounded with a hierarchy of widths and extrinsic curvatures. We show how the manifold boundary approximation can extract the simple, hidden theory from complicated sloppy models. We attribute the success of simple effective models in physics as likewise emerging from complicated processes exhibiting a low effective dimensionality. We discuss the ramifications and consequences of sloppy models for biochemistry and science more generally. We suggest that the reason our complex world is understandable is due to the same fundamental reason: simple theories of macroscopic behavior are hidden inside complicated microscopic processes.EigenvalueInformation geometryLeast squaresGeodesicRenormalization groupDiffusion equationNeural networkEffective theoryLevenberg-Marquardt algorithmDegree of freedom...
- Hubble's announcement of the magnitude-redshift relation \cite{Hub29} brought about a major change in our understanding of the Universe. After tracing the pre-history of Hubble's work, and the hiatus in our understanding which his underestimate of distances led to, this review focuses on the development and success of our understanding of the expanding universe up to the present day, and the part which General Relativity plays in that success.GalaxyNebulaeFriedmann-Lemaitre-Robertson-Walker metricStarAndromeda galaxyCosmic microwave backgroundSunGeneral relativityStatic universeCurvature...
- The structure and dark matter halo core properties of dwarf spheroidal galaxies (dSphs) are investigated. A double-isothermal model of an isothermal stellar system, embedded in an isothermal dark halo core provides an excellent fit to the various observed stellar surface density distributions. The stellar system can be well characterised by King profiles with a broad distribution of concentration parameters c. The core scale length of the stellar system a_* is sensitive to the central dark matter density rho_0. In contrast to single-component systems, the cut-off radius of the stellar system, rs_t, however does not trace the tidal radius but the core radius r_c of its dark matter halo. c is therefore sensitive to the ratio of the stellar to the dark matter velocity dispersion, sigma_*/sigma_0. Simple empirical relationships are derived that allow to calculate the dark halo core parameters rho_0, r_c and sigma_0, given the observable quantities sigma_*, a_* and c. The DIS model is applied to the Milky Way's dSphs. Their halo velocity dispersions lie in a narrow range of 10km/s <= sigma_0 <= 18km/s with halo core radii of 280pc <= r_c <= 1.3kpc and r_c=2a_*. All dSphs follow closely the same universal dark halo core scaling relation rho_0*r_c=75 Msolar/pc^2 that characterises the cores of more massive galaxies over several orders of magnitude in mass. The dark matter core mass is a strong function of core radius. Inside a fixed radius r_u, with r_u the logarithmic mean of the dSph's core radii, the total enclosed mass M_u is however roughly constant, although outliers should exist. For our dSphs we find r_u=400pc and M_u=2.6*10^7 Msolar. The core densities of the Galaxy's dSphs are very high, with rho_0=0.2 Msolar/pc^3. They should therefore be tidally undisturbed. Observational evidence for tidal effects might then provide a serious challenge for the cold dark matter scenario.StarKing modelKinematicsCold dark matterRotation CurveStar systemsStellar velocity dispersionHost galaxyMilky WayCarina Dwarf...
- The abundance of galaxy clusters is in principle a powerful tool to constrain cosmological parameters, especially $\Omega_\mathrm{m}$ and $\sigma_8$, due to the exponential dependence in the high-mass regime. While the best observables are the X-ray temperature and luminosity, the abundance of galaxy clusters, however, is conventionally predicted as a function of mass. Hence, the intrinsic scatter and the uncertainties in the scaling relations between mass and either temperature or luminosity lower the reliability of galaxy clusters to constrain cosmological parameters. In this article we further refine the X-ray temperature function for galaxy clusters by Angrick et al., which is based on the statistics of perturbations in the cosmic gravitational potential and proposed to replace the classical mass-based temperature function, by including a refined analytic merger model and compare the theoretical prediction to results from a cosmological hydrodynamical simulation. Although we find already a good agreement if we compare with a cluster temperature function based on the mass-weighted temperature, including a redshift-dependent scaling between mass-based and spectroscopic temperature yields even better agreement between theoretical model and numerical results. Incorporating this additional scaling in our model, we constrain the cosmological parameters $\Omega_\mathrm{m}$ and $\sigma_8$ from an X-ray sample of galaxy clusters and find agreement with the recent CMB-based results from the Planck mission at 1$\sigma$-level.Numerical simulationCosmologyDark matterMatter power spectrumVirial theoremThermalisationHydrodynamical simulationsHomogenizationCritical densityCosmic microwave background...
- We investigate the angular and kinematic distributions of satellite galaxies around a large sample of bright isolated primaries in the spectroscopic and photometric catalogues of the Sloan Digital Sky Survey (SDSS). We detect significant anisotropy in the spatial distribution of satellites. To test whether this anisotropy could be related to the rotating disks of satellites recently found by Ibata et al. in a sample of SDSS galaxies, we repeat and extend their analysis. Ibata et al. found an excess of satellites on opposite sides of their primaries having anticorrelated radial velocities. We find that this excess is sensitive to small changes in the sample selection criteria which can greatly reduce its significance. In addition, we find no evidence for correspondingly correlated velocities for satellites observed on the same side of their primaries, which would be expected for rotating disks of satellites. We conclude that the detection of coherent rotation in the satellite population in current observational samples is not robust. We compare our data to the $\Lambda$CDM Millennium simulations populated with galaxies according to the semi-analytic model of Guo et al. We find excellent agreement with the spatial distribution of satellites in the SDSS data and the lack of a strong signal from coherent rotation.EllipticityFriends of friends algorithmLocal groupMilky WayLine of sight velocityAccretionSemi-analytical model of galaxy formationSloan Digital Sky SurveyStatisticsSpectroscopic redshift...
- Galaxy cluster Abell 3827 hosts the stellar remnants of four almost equally bright elliptical galaxies within a core of radius 10kpc. Such corrugation of the stellar distribution is very rare, and suggests recent formation by several simultaneous mergers. We map the distribution of associated dark matter, using new Hubble Space Telescope imaging and VLT/MUSE integral field spectroscopy of a gravitationally lensed system threaded through the cluster core. We find that each of the central galaxies retains a dark matter halo, but that (at least) one of these is spatially offset from its stars. The best-constrained offset is 1.62+/-0.48kpc, where the 68% confidence limit includes both statistical error and systematic biases in mass modelling. Such offsets are not seen in field galaxies, but are predicted during the long infall to a cluster, if dark matter self-interactions generate an extra drag force. With such a small physical separation, it is difficult to definitively rule out astrophysical effects operating exclusively in dense cluster core environments - but if interpreted solely as evidence for self-interacting dark matter, this offset implies a cross-section sigma/m=(1.7+/-0.7)x10^{-4}cm^2/g x (t/10^9yrs)^{-2}, where t is the infall duration.Strong gravitational lensingMonte Carlo Markov chainStar formationMass distributionIntra-cluster lightEllipticitySelf-interaction cross-sectionGalactic haloStatistical errorInitial mass function...
- We present an introductory discussion of deep-inelastic lepton-proton scattering as a means to probe the substructure of the proton. A resume of QCD is given, emphasizing the running of the coupling constant and the DGLAP evolution equations for the parton densities. The determination of parton distributions is discussed and their importance for predictions of processes at the LHC is emphasized. Going beyond the pure DGLAP regime, we briefly discuss the behaviour of parton densities at low x, and the evidence for non-linear absorptive contributions.QuarkPartonQuantum chromodynamicsHadronizationFlavourQuantum electrodynamicsEvolution equationPerturbative QCDAbsorptivityPomeron...
- The extreme physical conditions of Gamma Ray Bursts can constitute a useful observational laboratory to test theories of gravity where very high curvature regimes are involved. Here we propose a sort of curvature engine capable, in principle, of explaining the huge energy emission of Gamma Ray Bursts. Specifically, we investigate the emission of radiation by charged particles non-minimally coupled to the gravitational background where higher order curvature invariants are present. The coupling gives rise to an additional force inducing a non-geodesics motion of particles. This fact allows a strong emission of radiation by gravitationally accelerated particles. As we will show with some specific model, the energy emission is of the same order of magnitude of that characterizing the Gamma Ray Burst physics. Alternatively, strong curvature regimes can be considered as a natural mechanism for the generation of highly energetic astrophysical events.Gamma ray burstFireballsNeutron starCosmologyGeneral relativitySupernovaSchwarzschild radiusCurvature tensorCurvatureBlack hole...
- Observed kinematical data of 40 Local Group (LG) members are used to derive the dark matter halo mass of such galaxies. Haloes are selected from the theoretically expected LG mass function and two different density profiles are assumed, a standard universal cuspy model and a mass dependent profile which accounts for the effects of baryons in modifying the dark matter distribution within galaxies. The resulting relations between stellar and halo mass are compared with expectations from abundance matching. Using a universal cuspy profile, the ensemble of LG galaxies is fit in relatively low mass haloes, leaving "dark" many massive haloes of \mhalo$\gtrsim$10$^{10}$\msun: this reflects the "too big to fail" problem and results in a \mstar-\mhalo\ relation that differs from abundance matching predictions. Moreover, the star formation efficiency of isolated LG galaxies increases with decreasing halo mass when adopting a cuspy model. By contrast, using the mass dependent density profile, dwarf galaxies with \mstar$\gtrsim$10$^{6}$\msun are assigned to more massive haloes, which have a central cored distribution of dark matter: the "too big to fail" problem is alleviated, the resultant \mstar-\mhalo\ relation follows abundance matching predictions down to the completeness limit of current surveys, and the star formation efficiency of isolated members decreases with decreasing halo mass, in agreement with theoretical expectations. Finally, the cusp/core space of LG galaxies is presented, providing a framework to understand the non-universality of their density profiles.Navarro-Frenk-White profileStellar massMilky WayHalo mass functionSatellite galaxyInner slopeAndromeda galaxyHalf-light radiusReionizationStar...
- The dwarf spheroidal galaxies (dSph) of the Milky Way are among the most attractive targets for indirect searches of dark matter. In this work, we reconstruct the dark matter annihilation (J-factor) and decay profiles for the newly discovered dSph Reticulum~II. This is done using an optimized spherical Jeans analysis of kinematic data obtained from the Michigan/Magellan Fiber System (M2FS). We find Reticulum~II to have one of the highest J-factor when compared to the other Milky Way dSphs. We have also checked the robustness of this result against several ingredients of the analysis. Unless it suffers from tidal disruption or significant inflation of its velocity dispersion from binary stars, Reticulum~II may provide a unique window on dark matter particle properties.Dark matterStarDark matter annihilationDwarf spheroidal galaxyDark matter particleDark Matter Density ProfileStellar kinematicsLikelihood functionDark matter haloPoint source...
- Simulations of the formation of large-scale structure predict that dark matter, low density highly ionized gas, and galaxies form 10 40 Mpc scale filaments. These structure are easily recognized in the distribution of galaxies, but have not been directly observed in the distribution of the gas. We use Ly-alpha absorption lines in the spectra of 24 AGN to present a new way to probe these filaments. We use a new catalogue of nearby (cz<10,000 km/s) galaxies, complete down to a luminosity of about 0.05 L* for the region of space analyzed here. Using HST spectra of 24 AGN we sample the gas associated with a 30x5 Mpc galaxy filament at cz~3500 km/s. All of our sightlines pass outside the virial radius of any known filament galaxy. Within 500 kpc of the filament axis the detection rate is ~80%, while no detections are seen more than 2.1 Mpc from the filament. The width of the Lya lines correlates with filament impact parameter and the four BLAs in our sample all occur within 400 kpc of the filament axis, indicating increased temperature and/or turbulence. Comparing to simulations, we find that the recent Haardt & Madau (2012) extragalactic ionizing background predicts a factor 3-5 too few ionizing photons. Using a more intense radiation field matches the hydrogen density profile within 2.1 Mpc of the filament axis, but the simulations still overpredict the detection rate between 2.1 and 5 Mpc from the axis.AbsorbanceIntergalactic mediumEquivalent widthAbsorptivityGalactic haloCosmic Origins SpectrographStatisticsStarQuasarSloan Digital Sky Survey...
- In these lectures we first concentrate on the cosmological problems which, hopefully, have to do with the new physics to be probed at the LHC: the nature and origin of dark matter and generation of matter-antimatter asymmetry. We give several examples showing the LHC cosmological potential. These are WIMPs as cold dark matter, gravitinos as warm dark matter, and electroweak baryogenesis as a mechanism for generating matter-antimatter asymmetry. In the remaining part of the lectures we discuss the cosmological perturbations as a tool for studying the epoch preceeding the conventional hot stage of the cosmological evolution.RecombinationPrimordial density perturbationDark energyThermalisationBaryon asymmetry of the UniverseHorizonStandard ModelSuperpartnerThe early UniverseExpansion of the Universe...
- In this paper a demand time series is analysed to support Make-To-Stock (MTS) and Make-To-Order (MTO) production decisions. Using a purely MTS production strategy based on the given demand can lead to unnecessarily high inventory levels thus it is necessary to identify likely MTO episodes. This research proposes a novel outlier detection algorithm based on special density measures. We divide the time series' histogram into three clusters. One with frequent-low volume covers MTS items whilst a second accounts for high volumes which is dedicated to MTO items. The third cluster resides between the previous two with its elements being assigned to either the MTO or MTS class. The algorithm can be applied to a variety of time series such as stationary and non-stationary ones. We use empirical data from manufacturing to study the extent of inventory savings. The percentage of MTO items is reflected in the inventory savings which were shown to be an average of 18.1%.Gaussian distributionHierarchical clusteringRegularizationMarketTime SeriesCustomer ServiceDecision makingFactorisationTaxonomyVolatiles...
- Many observations suggest that much of the matter of the universe is non-baryonic. Recently, the DAMA NaI dark matter direct detection experiment reported an annual modulation in their event rate consistent with a WIMP relic. However, the Cryogenic Dark Matter Search (CDMS) Ge experiment excludes most of the region preferred by DAMA. We demonstrate that if the dark matter can only scatter by making a transition to a slightly heavier state (Delta m ~ 100kev), the experiments are no longer in conflict. Moreover, differences in the energy spectrum of nuclear recoil events could distinguish such a scenario from the standard WIMP scenario. Finally, we discuss the sneutrino as a candidate for inelastic dark matter in supersymmetric theories.DAMA/LIBRACDMS experimentWeakly interacting massive particleDark matterInelastic Dark MatterElasticitySunCosmologyNeutrinoRelic abundance...
- Soon after the postulation of quarks, it was suggested that they interact via gluons, but direct experimental evidence was lacking for over a decade. In 1976, Mary Gaillard, Graham Ross and the author suggested searching for the gluon via 3-jet events due to gluon bremsstrahlung in $e^+ e^-$ collisions. Following our suggestion, the gluon was discovered at DESY in 1979 by TASSO and the other experiments at the PETRA collider.Quantum chromodynamicsQCD jetThree jet eventHadronizationPartonStrong interactionsYang-Mills theoryCERNField theoryAsymptotic freedom...
- This pedagogical review of galaxy cluster simulations is based on three lectures given at the 2008 Enrico Fermi Summer School entitled "Astrophysics of Galaxy Clusters". It covers the standard cosmological framework, growth of perturbations in the linear regime, analytic models for nonlinear perturbation growth, statistics of galaxy cluster populations, virial scaling relations, overview of numerical methods, simulating gas in galaxy clusters, basic results on adiabatic clusters (Santa Barbara cluster comparison project), effect of additional physics, recent progress in galaxy clustering modeling (Galcons, turbulence, AGN jets, cluster-wide B-fields), simulating statistical samples and lightcones, and simulated SZE surveys.Cluster of galaxiesCosmologyMatter power spectrumGalaxyTurbulenceSunyaev-Zel'dovich effectAdaptive mesh refinementStar formationIntra-cluster mediumDark matter...
- The measurement of the invisible Z-boson decay width at e+e- colliders can be done "indirectly", by subtracting the Z-boson visible partial widths from the Z-boson total width, or "directly", from the process e+e- -> \gamma \nu \bar{\nu}. Both procedures are sensitive to different types of new physics and provide information about the couplings of the neutrinos to the Z-boson. At present, measurements at LEP and CHARM II are capable of constraining the left-handed Z\nu\nu-coupling, 0.45 <~ g_L <~ 0.5, while the right-handed one is only mildly bounded, |g_R| <= 0.2. We show that measurements at a future e+e- linear collider at different center-of-mass energies, \sqrt{s} = MZ and \sqrt{s}s ~ 170 GeV, would translate into a markedly more precise measurement of the Z\nu\nu-couplings. A statistically significant deviation from Standard Model predictions will point toward different new physics mechanisms, depending on whether the discrepancy appears in the direct or the indirect measurement of the invisible Z-width. We discuss some scenarios which illustrate the ability of different invisible Z-boson decay measurements to constrain new physics beyond the Standard Model.Standard ModelLarge Electron-Positron ColliderNeutrinoMissing massSystematic errorStatisticsStatistical errorL3Z bosonCharged lepton...
- We examine the claimed excess X-ray line emission near 3.5 keV including both a new analysis of XMM-Newton observations of the Milky Way center and a reanalysis of the data on M~31 and clusters. In no case do we find conclusive evidence for an excess. In the case of the Galactic center we show that known plasma lines, including in particular K XVIII lines at 3.48 and 3.52 keV, provide a satisfactory fit to the XMM data. We estimate the expected flux of the K XVIII lines and find that the measured line flux falls squarely within the predicted range based on the brightness of other well-measured lines in the energy range of interest and on detailed multi-temperature plasma models. We then re-assess the evidence for excess emission from clusters of galaxies, allowing for systematic uncertainty in the expected flux from known plasma lines and additional uncertainty due to potential variation in the abundances of different elements. We find that no conclusive excess line emission can be advocated when considering systematic uncertainties in Perseus or in other clusters. We also re-analyze the XMM data for M~31 and find no statistically significant line emission near 3.5 keV to a level greater than one sigma. Finally, we analyze the Tycho supernova remnant, which shows similar plasma features to the sources above, but does not host any significant dark matter. We detect a 3.55 keV line from Tycho, which points to possible systematic effects in the flux determination of weak lines, or to relative elemental abundances vastly different from theoretical expectations.EPIC PN cameraXMM-Newton MOS cameraOverabundanceGalactic CenterDark matter decayThermalisationSterile neutrinoSystematic errorField of viewGalaxy...
- In this chapter we provide an overview of the science enabled by radio continuum surveys in the SKA era, focusing on galaxy/galaxy cluster physics and evolution studies, and other relevant continuum science in the >2020 scientific framework. We outline a number of 'reference' radio-continuum surveys for SKA1 that can address such topics, and comprehensively discuss the most critical science requirements that we have identified. We highlight what should be achieved by SKA1, to guarantee a major leap forwards with respect to the pre-SKA era, considering the science advances expected in the coming years with existing and upcoming telescopes (JVLA, LOFAR, eMERLIN, and the three SKA precursors: MWA, ASKAP and MeerKAT). In this exercise we take in due account also the other waveband facilities coming online at the same time (e.g. Euclid, LSST, etc.), which tackle overlapping scientific goals, but in a different manner. In this respect particular attention has been payed to ensure that the proposed reference surveys are able to exploit the existing synergies with such facilities, so as to generate strong involvement from all astronomical communities, and leave a lasting legacy value. It is clear that a certain degree of freedom is allowed to some of the observational parameters. We believe it is very important to best fine-tune such parameters taking into proper account existing commensalities with SKA1 surveys addressing other science areas (HI galaxy science, magnetism, cosmology).Active Galactic NucleiGalactic evolutionThermalisationStar formation rateStar formationAll-sky surveyAccretionGravitational lensingMultidimensional ArraySynchrotron radiation...
- We present Magellan/M2FS, VLT/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8 +/- 0.5 km/s and a velocity dispersion of 3.3 +/- 0.7 km/s. The mass-to-light ratio of Ret II within its half-light radius is 470 +/- 210 Msun/Lsun, demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 km/s, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 +/- 0.09 dex, and we identify several extremely metal-poor stars with [Fe/H] < -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a mean metallicity of [Fe/H] = -2.65 +/- 0.07, Ret II matches Segue~1 as the most metal-poor galaxy known. Although Ret II is the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of the dark matter density squared is log J = 18.8 +/- 0.6 Gev^2/cm^5 within 0.2 degrees, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies.The Dark Energy SurveySpectrographsCalibrationTwilightDark matter haloForeground starHorizontal branch starKinematicsMonte Carlo methodAbsorption line...
- We introduce a novel method for weak-lensing measurements, which is based on a mathematically exact deconvolution of the moments of the apparent brightness distribution of galaxies from the telescope's PSF. No assumptions on the shape of the galaxy or the PSF are made. The (de)convolution equations are exact for unweighted moments only, while in practice a compact weight function needs to be applied to the noisy images to ensure that the moment measurement yields significant results. We employ a Gaussian weight function, whose centroid and ellipticity are iteratively adjusted to match the corresponding quantities of the source. The change of the moments caused by the application of the weight function can then be corrected by considering higher-order weighted moments of the same source. Because of the form of the deconvolution equations, even an incomplete weighting correction leads to an excellent shear estimation if galaxies and PSF are measured with a weight function of identical size. We demonstrate the accuracy and capabilities of this new method in the context of weak gravitational lensing measurements with a set of specialized tests and show its competitive performance on the GREAT08 challenge data. A complete C++ implementation of the method can be requested from the authors.GalaxyPoint spread functionWeight functionEllipticityWeak lensingTelescopesGravitational lensingStatisticsSystematic errorMultipole moments...
- We performed the deepest search for an X-ray emission line between 0.5 and 7 keV from non-baryonic dark matter with the Suzaku XIS. Dark matter associated with the Milky Way galaxy was selected as the target to obtain the best signal-to-noise ratio. From the Suzaku archive, we selected 187 data sets of blank sky regions which were dominated by the X-ray diffuse background. The data sets were from 2005 to 2013. Instrumental responses were adjusted by multiple calibration data sets of the Crab Nebula. We also improved the technique of subtracting lines of instrumental origin. These energy spectra were well described by X-ray emission due to charge exchange around the Solar System, hot plasma in and around the Milky Way and superposition of extra-galactic point sources. A signal of a narrow emission line was searched for, and the significance of detection was evaluated in consideration of the blind search method (the Look-elsewhere Effect). Our results exhibited no significant detection of an emission line feature from dark matter. The 3$\sigma$ upper limit for the emission line intensity between 1 and 7 keV was $\sim10^{-2}$ photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$, or $\sim 5\times10^{-4}$ photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ per $M_\odot$ pc$^{-2}$, assuming a dark matter distribution with the Galactic rotation curve. The parameters of sterile neutrinos as candidates of dark matter were also constrained.Dark matterAPEC plasma modelStatistical errorLocal Hot BubbleCosmic X-ray backgroundCluster of galaxiesCollisional ionization equilibriumThermalisationMilky Way haloX-ray observatory...
- In this paper, the notion of local algebraic fundamental groups of normal complex analytic singularities are generalized to certain profinite groups called $D$-local algebraic fundamental groups which turns out to be useful even for the study of usual local algebraic fundamental groups and the Lefshetz type theorem for $D$-local algebraic fundamental groups is proved under certain conditions. The theorem yields, for example, the finiteness of the local algebraic fundamental groups of a certain class of four dimensional singularities and will be useful for the classification of three dimensional purely log terminal singularities.HomomorphismComplex analytic spaceTopological invariantClassificationCovarianceTerminal singularityFinite morphismExceptional divisorSubgroupExact sequence...
- In this paper, the Euler characteristic formula for projective logarithmic minimal degenerations of surfaces with Kodaira dimension zero over a 1-dimensional complex disk is proved under a reasonable assumption and as its application, the singularity of logarithmic minimal degenerations are determined in the abelian or hyperelliptic case. By globalizing this local analysis of singular fibres via generalized canonical bundle formulae due to Fujino-Mori, we bound the number of singular fibres of abelian fibred Calabi-Yau threefolds from above,which was previously done by Oguiso in the potentially good reduction case.Minimal modelsMorphismFibrationEuler characteristicEuler numberIsomorphismComplex analytic spaceCanonical bundleTerminal singularityElliptic curve...
- Neutrinos propagating in media (matter and electromagnetic fields) undergo flavor and helicity oscillations, where helicity transitions are instigated both by electromagnetic fields and matter currents. In addition, it has been shown that correlations between neutrinos and antineutrinos of opposite momentum can build up in anisotropic media. We re-derive the neutrino equations of motion in the mean-field approximation for homogeneous yet anisotropic media, confirming previous results except for a small correction in the Majorana case. Furthermore, we derive the mean-field Hamiltonian induced by neutrino electromagnetic interactions. We also provide a phenomenological discussion of pair correlations in comparison with helicity correlations.SupernovaMajorana neutrinoDensity matrixForm factorNeutrino massKinetic equationLepton flavour violationDirac neutrinoWeak neutral current interactionCreation and annihilation operators...
- This is a brief rebuttal to arXiv:1502.03821, which claims to provide the first observational proof of dark matter interior to the solar circle. We point out that this result is not new, and can be traced back at least a quarter century.Dark matterRotation CurveSunStatisticsStarGalaxyRandom errorSystematic errorStellar diskSolar radius...
- Sterile neutrinos of keV masses are one of the most promising candidates for the warm dark matter, which could solve the small-scale problems encountered in the scenario of cold dark matter. We present a detailed study of the production of such sterile neutrinos in a supernova core, and derive stringent bounds on the active-sterile neutrino mixing angles and sterile neutrino masses based on the standard energy-loss argument.NeutrinoMixing angleSupernovaAntineutrinoThermalisationWarm dark matterVacuum mixing angleLepton numberEvolution equationGalaxy...
- All commonly considered dark matter scenarios are based on hypothetical particles with small but non-zero thermal velocities and tiny interaction cross-sections. A generic consequence of these attributes is the suppression of small-scale matter perturbations either due to free-streaming or due to interactions with the primordial plasma. The suppression scale can vary over many orders of magnitude depending on particle candidate and production mechanism in the early Universe. While nonlinear structure formation has been explored in great detail well above the suppression scale, the range around suppressed perturbations is still poorly understood. In this paper we study structure formation in the regime of suppressed perturbations using both analytical techniques and numerical simulations. We develop simple and theoretically motivated recipes for the halo mass function, the expected number of satellites, and the halo concentrations, which are designed to work for power spectra with suppression at arbitrary scale and of arbitrary shape. As case studies, we explore warm and mixed dark matter scenarios where effects are most distinctive. Additionally, we examine the standard dark matter scenario based on weakly interacting massive particles (WIMP) and compare it to pure cold dark matter with zero primordial temperature. We find that our analytically motivated recipes are in good agreement with simulations for all investigated dark matter scenarios, and we therefore conclude that they can be used for generic cases with arbitrarily suppressed small-scale perturbations.Dark matterCold dark matterWarm dark matterCollapse redshiftExtended Press-Schechter formalismMixed dark matterConcentration-mass relationMatter power spectrumVirial massCosmology...
- A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density...Lowest Landau LevelLandau levelQuantum chromodynamicsQuantum electrodynamicsFermion propagatorNambu-Jona-Lasinio modelCoupling constantSelf-energyStrong magnetic fieldQuark...
- We concisely review the recent evolution in the study of parafermions -- exotic emergent excitations that generalize Majorana fermions and similarly underpin a host of novel phenomena. First we illustrate the intimate connection between Z_3-symmetric "spin" chains and one-dimensional parafermion lattice models, highlighting how the latter host a topological phase featuring protected edge zero modes. We then tour several blueprints for the laboratory realization of parafermion zero modes -- focusing on quantum Hall/superconductor hybrids, quantum Hall bilayers, and two-dimensional topological insulators -- and describe striking experimental fingerprints that they provide. Finally, we discuss how coupled parafermion arrays in quantum Hall architectures yield topological phases that potentially furnish hardware for a universal, intrinsically decoherence-free quantum computer.AnyonSuperconductivitySuperconductorChiralityHamiltonianCondensationDomain wallBackscatteringFerromagnetismCooper pair...
- We construct a model of quantum metrology inspired by the computational model known as deterministic quantum computation with one quantum bit (DQC1). Using only one pure qubit together with $l$ fully-mixed qubits we obtain measurement precision at the standard quantum limit, which is typically obtained using the same number of uncorrelated qubits in fully-pure states. The standard quantum limit can be exceeded using an additional qubit, which adds only a small amount of purity. We show that the discord in the final state vanishes only in the limit of attaining infinite precision for the parameter being estimated.EntanglementFisher informationEigenvalueQubitPOVMUnitary transformationUnitary operatorQuantum technologyQuantum discordLOCC...