# Posters

This is the list of posters presented at the posters session that will take place during the school (See Schedule). The posters will be displayed during all the school.

### Preliminary list of posters (will be updated regularly).

Posters can be printed in A2 format (easy to bring with you). No on-site printing service is available.

Click on “abstract” for displaying and hiding individual abstracts.

Corentin Cadiou (IAP) The influence of the cosmic web on assembly bias

We present an extension of the excursion-set theory presented in [1] and originally formulated by [2] by taking into account the large-scale perturbations induced by nearby protofilaments defined as saddle point in the potential field. The mass, accretion rate and formation time of dark matter haloes are analytically predicted. The model predicts that at fixed mass, mass accretion rate and formation vary with orientation and distance from the saddle, demonstrating the indeed assembly bias is influenced by the large-scale tides. Our results are in agreement with recent observations of [3] and provide a new framework to compute the effects of the large scale anisotropy on halo populations.

References

[1] Musso, M, C Cadiou, C Pichon, S Codis, K Kraljic, and Y Dubois, How Does the Cosmic Web Impact Assembly Bias?, Monthly Notices of the Royal Astronomical Society 476, no. 4 (June 1, 2018): 4877‚Äì4906. https://doi.org/10.1093/mnras/sty191.

[2] Press, William H., and Paul Schechter, Formation of Galaxies and Clusters of Galaxies by Self-Similar Gravitational Condensation., The Astrophysical Journal 187 (February 1974): 425‚Äì425. https://doi.org/10.1086/152650.

[3] Kraljic, K., S. Arnouts, C. Pichon, C. Laigle, S De Torre, D. Vibert, C. Cadiou, et al, Galaxy Evolution in the Metric of the Cosmic Web, 000, no. October (2017). https://arxiv.org/abs/1710.02676.

plenary-session-2 Poster Session
Isabella Paola Carucci (UCL) Cosmology with 21cm intensity mapping: disentangling dark matter and dark energy models

The nature of the most abundant components of the Universe, dark energy and dark matter, is still to be uncovered. What can be learned considering the 21cm radiation observed with the intensity mapping (IM) technique? This poster shortly present the 21cm IM, i.e. what kind of signal it is, then shows how it varies when competitive and realistic dark energy and dark matter scenarios are at play. The focus is on how distinctive and detectable these effects are, presenting forecasts for the bounds that a radio telescope like the Square Kilometre Array (SKA) would be able to uniquely set.

References

[1] Isabella P. Carucci, Cosmology with 21cm intensity mapping, Journal of Physics: Conference Series, Volume 956, Issue 1, article id. 012003 (2018). [astro-ph.CO: 1712.04022].

[2] Isabella P. Carucci, Pier-Stefano Corasaniti and Matteo Viel, Imprints of non-standard Dark Energy and Dark Matter Models on the 21cm Intensity Map Power Spectrum, Journal of Cosmology and Astroparticle Physics, Issue 12, article id. 018 (2017). [astro-ph.CO: 1706.09462].

[3] Isabella P. Carucci, Francisco Villaescusa-Navarro, Matteo Viel and Andrea Lapi, Warm dark matter signatures on the 21cm power spectrum: Intensity mapping forecasts for SKA, Journal of Cosmology and Astroparticle Physics, Issue 07, article id. 047, (2015). [astro-ph.CO: 1502.06961].

plenary-session-2 Poster Session
Anaelle Halle (MPA) Phase-space structure analysis of self-gravitating collisionless spherical systems

This work is based on [1]. In the mean field limit, isolated gravitational systems often evolve towards a steady state through a violent relaxation phase. One question is to understand the nature of this relaxation phase, in particular the role of radial instabilities in the establishment/destruction of the steady profile. Here, through a detailed phase-space analysis based both on a spherical Vlasov solver, a shell code and a N-body code, we revisit the evolution of collisionless self-gravitating spherical systems with initial power-law density profiles $\rho(r) \propto r^n$, $0 \le n \le -1.5$, and Gaussian velocity dispersion. Two sub-classes of models are considered, with initial virial ratios $\eta = 0.5$ (“warm”) and $\eta = 0.1$ (“cool”). Thanks to the numerical techniques used and the high resolution of the simulations, our numerical analyses are able, for the first time, to show the clear separation between two or three well known dynamical phases: (i) the establishment of a spherical quasi-steady state through a violent relaxation phase during which the phase-space density displays a smooth spiral structure presenting a morphology consistent with predictions from self-similar dynamics, (ii) a quasi-steady state phase during which radial instabilities can take place at small scales and destroy the spiral structure but do not change quantitatively the properties of the phase-space distribution at the coarse grained level and (iii) relaxation to non spherical state due to radial orbit instabilities for $n \le -1$ in the cool case.

plenary-session-2 Poster Session
Hafiza Kausar (UCP) Cosmic Inflation in Hybrid Metric-Palatini Gravity

Hybrid metric-Palatini gravity theory is a newly proposed theory, whose action depend linearly on the metric scalar curvature and nonlinearly on the arbitrary function of Palatine scalar curvature. The fascinating property of this theory is to maintain all the positive results of GR at solar system and compact object scale as well as to add explanation to the recent cosmological observations. Looking at the recent popularity of this theory, we study the issue of cosmic inflation in this theory. For this purpose, we calculate the slow-roll parameter, scalar-to-tensor ratio and spectral index and then investigate their behavior graphically to check the growth of the universe. We also check our findings with the recent observational data

References

[1] Rosa, J. L., et al., Cosmological Solutions in Generalized Hybrid metric-Palatini gravity, Phys. Rev. D 95(2017)124035.

[2] Leanizbarrutia, I., et al., Crossing SNe 1a and BAO Observational Constraints with Local ones in Hybrid metric-Palatini gravity, Phys. Rev. D 95(2017)084046.

[3] Zubair, M. and Kousar, F., Inflationary Cosmology for Models with different Potentials, Can. J. Phys., 95(2017)1074.

plenary-session-2 Poster Session
Nassima Khaldi (USTOMB) Boundary value problems described by Drazin invertible operators

The main subject of this work is the study of a general linear boundary value problems with Drazin and right Drazin (resp. left Drazin) invertible operators and corresponding to initial boundary operators. The obtained results are then employed to solve Schrodinger equation equation.

References

[1] J. Behrndt and M. Langer, Boundary value problems for elliptic partial differential operators on bounded domains, J. Funct. Anal. 243 (2007), 536–565.

[2] J. Behrndt and M. Langer, Elliptic operators, Dirichlet-to-Neumann maps and quasi boundary triples, London Math. Soc. Lecture Note Series 404 (2012), 121–160.

[3] J. Behrndt, M. Langer, and V. Lotoreichik, Trace formulae and singular values of resolvent power differences of self-adjoint elliptic operators, J. London Math. Soc. 88 (2)(2013), 319-337.

[4] P.L. Butzer, J.J. Koliha, The a-Drazin inverse and ergodic behaviour of semigroups and cosine operator functions, J. Operator theory 62; 2(2009), 297-326.

[5] S.L. Campbell, C.D. MEYER, JR. and N.J. Rosef, Application of the Drazin inverse to linear systems of differential aquations with singular constant coefficients, SIAM J. Appl. Math. Vol. 31, No. 3, November 1976.

[6] M.P. Drazin, Pseudo-inverse in associative rings and semigroups, Amer, Math. Monthly 65(1958), 506-514.

[7] K.M.Houcine, M. Benharrat. and B. Messirdi, Left and right generalized Drazin invertible operators. Linear and Multilinear Algebra, 1-14.

[8] N. Khaldi, M. Benharrat. and B. Messirdi, On the Spectral Boundary Value Problems and Boundary Approximate Controllability of Linear Systems. Rend. Circ. Mat. Palermo, 63 (2014) 141-153.

[9] N. Khaldi, M.Benharrat. and B. Messirdi, spectral approach for solving boundary value matrix problems: existence, uniqueness and application to symplectic elasticity. J. Adv. Res. Appl. Math. (to appear).

[10] J. J. Koliha, T.D. Tran, The Drazin inverse for closed linear operators. preprint, 1998.

[11] J. J. Koliha, T.D. Tran, Closed semistable operators and singular differential equations, Czechoslovak Math. J, 53 (3) (2003), 605–620.

[12] J. J. Koliha, Trung Dinh Tran, The Drazin inverse for closed linear operators and the asymptotic convergence of $C_0$-semigroups, J. Operator theory 46 (2001), 323-336.

[13] N. V. Mau, Boundary value problems and controllability of linear systems with right invertible operators, Dissertationes Math, Warszawa 1992.

[14] M.Z. Nashed, Y. Zhao, The Drazin inverse for singular evolution equations and paratial differential operators, World Sci. Ser. Appl. Anal. 1(1992), 441-456.

[15] D. Przeworska-Rolewicz, Algebraic theory of right invertible operators, Studia Math. XLVIII (1973), 129-144.

[16] V. Ryzhov, Spectral Boundary Value Problems and their Linear Operators, Opuscula Mathematica, 27 (2) (2007), 305-331.

[17] V. Ryzhov, A Note on an Operator-Theoretic Approach to Classic Boundary Value Problems for Harmonic and Analytic Functions in Complex Plane Domains, Integr. Equ. Oper. Theory 67 (2010), 327–339.

[18] H. V. Thi, Approximate controllability for systems described by right invertible operators, Control and Cybernetics 37(1) (2008), 39–51.

plenary-session-2 Poster Session
Christina Kreisch (Princeton) Massive Neutrinos Leave Fingerprints on Cosmic Voids

Massive neutrinos uniquely affect cosmic voids. We explore their impact on void clustering using both the DEMNUni and MassiveNuS simulations. For voids, neutrino effects depend on the observational tracers. As neutrino mass increases, the number of small voids traced by cold dark matter particles increases and the number of large voids decreases. Surprisingly, when massive halos are used as tracers, we see the opposite effect. How neutrinos impact the scale at which voids cluster and the void correlation is similarly sensitive to the tracers. This scale dependent bias is not due to simulation volume or halo density. The interplay of these signatures in the void abundance and clustering leaves a distinct fingerprint that could be detected with observations and potentially help break degeneracies between different cosmological parameters. This paper paves the way to exploit cosmic voids in future surveys to constrain the mass of neutrinos.

plenary-session-2 Poster Session
Alex Malz (CCPP) Supernova Cosmology Inference with Probabilistic Photometric Redshifts

The Bayesian Estimation Applied to Multiple Species (BEAMS; [1]) framework employs probabilistic supernova (SN) classifications to estimate the Hubble parameter that quantifies the relationship between distance and redshift over cosmic time. However, it requires knowledge of the host galaxy spectroscopic redshifts, limiting its use in upcoming missions such as that of the Large Synoptic Survey Telescope (LSST) for which follow-up spectroscopy will be infeasible. Photometric redshifts (photo-$z$) point estimates suffer from significant bias, scatter, and outlier effects, making them unsuitable for precision SN cosmology. Photo-$z$ probability density functions (PDFs) appropriately encapsulate the nontrivial uncertainties, but there are few mathematically motivated methodologies that make use of the information. We build on one such mathematically motivated approach, the Cosmological Hierarchical Inference with Probabilistic Photometric Redshfts (CHIPPR; [2]) probabilistic graphical model and present Supernova Cosmology Inference with Probabilistic Photometric Redshifts (SCIPPR), a Bayesian hierarchical model that naturally melds the BEAMS and CHIPPR approaches to use both posterior PDFs of SN type, redshift, and distance modulus based on photometric lightcurve fits and posterior PDFs of redshift based on host galaxy photometry. By combining probabilistic data products in a fully self-consistent way, we infer a posterior PDF over the cosmological parameters in the absence of spectroscopic observations.

References

[1] M. Kunz, B.A. Bassett, and R. Hlozek, {Bayesian estimation applied to multiple species}. Phys. Rev. D 75 10 (2007) [doi:10.1103/PhysRevD.75.103508].

[2] A.I. Malz and D.W. Hogg, {Cosmological Hierarchical Inference with Probabilistic Photometric Redshifts (CHIPPR)}. in prep [https://github.com/aimalz/chippr/].

plenary-session-2 Poster Session
Brandon Melcher (SYR) Co-Decay Dark Matter: Structure and Primordial Black Hole Formation

We study the cosmological consequences of codecaying dark matter?a recently proposed mechanism for depleting the density of dark matter through the decay of nearly degenerate particles. A generic prediction of this framework is an early dark matter dominated phase in the history of the Universe, that results in the enhanced growth of dark matter perturbations on small scales. We compute the duration of the early matter dominated phase and show that the perturbations are robust against washout from free streaming. The enhanced small-scale structure is expected to survive today in the form of compact microhalos and can lead to significant boost factors for indirect-detection experiments, such as FERMI, where dark matter would appear as point sources [1]. Following [2], we also comment on the likelihood of primordial black hole formation.

References

[1] J. Dror, E. Kuflik, B. Melcher, and S. Watson, Concentrated dark matter: Enhanced small-scale structure from codecaying dark matter, Phys.Rev. D97 no. 6 (2018) [hep-ph/1711.04773].

[2] J. Georg and S. Watson: A Preferred Mass Range for Primordial Black Hole Formation and Black Holes as Dark Matter Revisited, JHEP 1709, 138 (2017) [astro-ph/1703.04825].

plenary-session-2 Poster Session
Artur Miroszewski (NCBJ) The role of internal clocks in early Universe cosmology

The basic tenet of the present work is the assumption of the lack of external and fixed time in the Universe. This assumption is best embodied by general relativity, which replaces the fixed space-time structure with the gravitational field, which is subject to dynamics. The lack of time does not imply the lack of evolution but rather brings to the forefront the role of internal clocks which are some largely arbitrary internal degrees of freedom with respect to which the evolution of timeless systems can be described. We take this idea seriously and try to understand what it implies for quantum mechanics when the fixed external time is replaced by an arbitrary internal clock.

References

[1] P. Malkiewicz and A. Miroszewski, Internal clock formulation of quantum mechanics, Phys. Rev. D 96 046003 (2017) (1706.00743 [gr-qc])

[2] E. Anderson, The Problem of Time: Quantum Mechanics Versus General Relativity, Fundamental Theories of Physics 170, Springer International Publishing (2017)

[3] K. Kuchar, Time and interpretation of quantum gravity, in Proceedings of the 4th Canadian Conference on General Relativity and Relativistic Astrophyscis, World Scientific, Singapore, (1992)

[4] Chris J. Isham, Canonical quantum gravity and the problem of time, Lectures presented at the NATO Advanced Study Institute: Recent Problems in Mathematical Physics, Salamanca, (1992)

plenary-session-2 Poster Session
Supranta Sarmaboruah (UW) Inferring the dark matter density with the spatial distribution of dark matter halos

Inferring the distribution of dark matter from the distribution of tracers such as galaxies and dark matter halos is one of the most important inference problem in current cosmology. It has far reaching consequences in accurate distance measurements using Baryon acoustic oscillations(BAOs), understanding the nature of dark matter, constraining modification of gravity on large-scales. However, this is a difficult task owing to our incomplete knowledge of structure formation on non-linear scales and biased formation of dark matter halos. However, with the advent of large-scale computing, clever algorithms and better understanding of structure formation, it is now possible to do a full forward-modelled Bayesian reconstruction of the large-scale structures. This has important advantages in that correlation of different measurement errors in inference are automatically incorporated in the analysis. Also, observational effects can be easily incorporated into the analytically modelled structure formation process. We are currently working to enhance the performance of these methods by using novel understanding of the biased formation of dark matter halos.

References

[1] Jens Jasche and Guilhem Lavaux, Physical Bayesian modelling of the non-linear matter distribution: new insights into the Nearby Universe, arXiv:1806.11117

[2] Jens Jasche and Benjamin D. Wandelt, Bayesian physical reconstruction of initial conditions from large scale structure surveys MNRAS 432:894, 2013.

[3] Supranta S. Boruah, Michael J. Hudson and Guilhem Lavaux, Bayesian forward modelling of the large scale structure using dark matter halos. In Preparation

plenary-session-2 Poster Session
Kimeel Sooknunan (UCT) Classification of Radio and Multiwavelength Transients with Machine Learning

With the advent of powerful telescopes such as the Square Kilometre Array (SKA), the Large Synoptic Survey Telescope (LSST) and the Laser Interferometer Gravitational-Wave Observatory (LIGO), we are entering a golden era of multimessenger transient astronomy. In order to cope with the dramatic increase in data volume, as well as successfully prioritise spectroscopic follow-up resources, we propose a new machine learning approach for the classification of radio transients. In this talk I will outline the algorithm's three main steps: (1) augmentation and interpolation of the data using Gaussian processes; (2) feature extraction using a wavelet decomposition; (3) classification with the popular machine learning algorithm random forests. I will present an application of our algorithm to existing radio transient data, illustrating its ability to accurately classify most radio transients after just 8 hours, and how performance is expected to increase as more training data is acquired. Finally, I will present a general approach for including multimessenger data for general transient classification, and demonstrate its effectiveness by showing the impact of incorporating a single optical data point into the analysis, which significantly reduces confusion.

plenary-session-2 Poster Session
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