Scholarly Works - Applied Mathematics and Theoretical PhysicsNo Descriptionhttps://www.repository.cam.ac.uk/handle/1810/2275072024-11-04T17:38:10Z2024-11-04T17:38:10Z5531Cylinders out of a top hat: Counts-in-cells for projected densitiesUhlemann, CPichon, CCodis, SL'Huillier, BKim, JBernardeau, FPark, CPrunet, Shttps://www.repository.cam.ac.uk/handle/1810/2802792024-01-07T06:50:10Z2018-06-21T00:00:00Zdc.title: Cylinders out of a top hat: Counts-in-cells for projected densities
dc.contributor.author: Uhlemann, C; Pichon, C; Codis, S; L'Huillier, B; Kim, J; Bernardeau, F; Park, C; Prunet, S
dc.description.abstract: © 2017 The Authors. Large deviation statistics is implemented to predict the statistics of cosmic densities in cylinders applicable to photometric surveys. It yields few per cent accurate analytical predictions for the one-point probability distribution function (PDF) of densities in concentric or compensated cylinders; and also captures the density dependence of their angular clustering (cylinder bias). All predictions are found to be in excellent agreement with the cosmological simulation Horizon Run 4 in the quasi-linear regime where standard perturbation theory normally breaks down. These results are combined with a simple local bias model that relates dark matter and tracer densities in cylinders and validated on simulated halo catalogues. This formalism can be used to probe cosmology with existing and upcoming photometric surveys like DES, Euclid or WFIRST containing billions of galaxies.
2018-06-21T00:00:00ZDark Energy Survey Year 1 Results: Photometric Data Set for CosmologyDrlica-Wagner, ASevilla-Noarbe, IRykoff, ESGruendl, RAYanny, BTucker, DLHoyle, BRosell, A CarneroBernstein, GMBechtol, KBecker, MRBenoit-Levy, ABertin, EKind, M CarrascoDavis, CVicente, J deDiehl, HTGruen, DHartley, WGLeistedt, BLi, TSMarshall, JLNeilsen, ERau, MMSheldon, ESmith, JTroxel, MAWyatt, SZhang, YAbbott, TMCAbdalla, FBAllam, SBanerji, MBrooks, DBuckley-Geer, EBurke, DLCapozzi, DCarretero, JCunha, CED'Andrea, CBCosta, LN daDePoy, DLDesai, SDietrich, JPDoel, PEvrard, AENeto, A FaustiFlaugher, BFosalba, PFrieman, JGarcia-Bellido, JGerdes, DWGiannantonio, TGschwend, JGutierrez, GHonscheid, KJames, DJJeltema, TKuehn, KKuhlmann, SKuropatkin, NLahav, OLima, MLin, HMaia, MAGMartini, PMcMahon, RGMelchior, PMenanteau, FMiquel, RNichol, RCOgando, RLCPlazas, AARomer, AKRoodman, ASanchez, EScarpine, VSchindler, RSchubnell, MSmith, MSmith, RCSoares-Santos, MSobreira, FSuchyta, ETarle, GVikram, VWalker, ARWechsler, RHZuntz, Jhttps://www.repository.cam.ac.uk/handle/1810/2799772023-12-21T06:38:16Z2018-01-01T00:00:00Zdc.title: Dark Energy Survey Year 1 Results: Photometric Data Set for Cosmology
dc.contributor.author: Drlica-Wagner, A; Sevilla-Noarbe, I; Rykoff, ES; Gruendl, RA; Yanny, B; Tucker, DL; Hoyle, B; Rosell, A Carnero; Bernstein, GM; Bechtol, K; Becker, MR; Benoit-Levy, A; Bertin, E; Kind, M Carrasco; Davis, C; Vicente, J de; Diehl, HT; Gruen, D; Hartley, WG; Leistedt, B; Li, TS; Marshall, JL; Neilsen, E; Rau, MM; Sheldon, E; Smith, J; Troxel, MA; Wyatt, S; Zhang, Y; Abbott, TMC; Abdalla, FB; Allam, S; Banerji, M; Brooks, D; Buckley-Geer, E; Burke, DL; Capozzi, D; Carretero, J; Cunha, CE; D'Andrea, CB; Costa, LN da; DePoy, DL; Desai, S; Dietrich, JP; Doel, P; Evrard, AE; Neto, A Fausti; Flaugher, B; Fosalba, P; Frieman, J; Garcia-Bellido, J; Gerdes, DW; Giannantonio, T; Gschwend, J; Gutierrez, G; Honscheid, K; James, DJ; Jeltema, T; Kuehn, K; Kuhlmann, S; Kuropatkin, N; Lahav, O; Lima, M; Lin, H; Maia, MAG; Martini, P; McMahon, RG; Melchior, P; Menanteau, F; Miquel, R; Nichol, RC; Ogando, RLC; Plazas, AA; Romer, AK; Roodman, A; Sanchez, E; Scarpine, V; Schindler, R; Schubnell, M; Smith, M; Smith, RC; Soares-Santos, M; Sobreira, F; Suchyta, E; Tarle, G; Vikram, V; Walker, AR; Wechsler, RH; Zuntz, J
dc.description.abstract: We describe the creation, content, and validation of the Dark Energy Survey (DES) internal year-one cosmology data set, Y1A1 GOLD, in support of upcoming cosmological analyses. The Y1A1 GOLD data set is assembled from multiple epochs of DES imaging and consists of calibrated photometric zero-points, object catalogs, and ancillary data products—e.g., maps of survey depth and observing conditions, star–galaxy classification, and photometric redshift estimates—that are necessary for accurate cosmological analyses. The Y1A1 GOLD wide-area object catalog consists of $\sim 137$ million objects detected in co-added images covering $\sim 1800\,{\deg }^{2}$ in the DES grizY filters. The 10σ limiting magnitude for galaxies is $g=23.4$, $r=23.2$, $i=22.5$, $z=21.8$, and $Y=20.1$. Photometric calibration of Y1A1 GOLD was performed by combining nightly zero-point solutions with stellar locus regression, and the absolute calibration accuracy is better than 2% over the survey area. DES Y1A1 GOLD is the largest photometric data set at the achieved depth to date, enabling precise measurements of cosmic acceleration at z lesssim 1.
2018-01-01T00:00:00ZAnalytic solutions for reduced leading-edge noise aerofoilsAyton, LJParuchuri, Chttps://www.repository.cam.ac.uk/handle/1810/2791002023-12-21T01:58:16Z2018-06-25T00:00:00Zdc.title: Analytic solutions for reduced leading-edge noise aerofoils
dc.contributor.author: Ayton, LJ; Paruchuri, C
dc.description.abstract: This paper presents an analytic solution for the sound generated by an unsteady gust interacting with a semi-infinite flat plate with a piecewise linear periodic leading edge. The Wiener-Hopf method is used in conjunction with a non-orthogonal coordinate transformation and separation of variables to allow analytical progress. A fully analytic solution is obtained in terms of a modal expansion for the far-field noise which is obtained by summing only a finite number of cuton modes, allowing very quick evaluation.
The analytic solution is compared to experimental results for five test case leading-edge geometries. Good agreement is seen indicating the analytic model is capturing the key features of the interaction such as the destructive interference from the tip and root. In four of the five test cases the serrated edges show large reductions of noise compared to the straight edge at mid and high frequencies, however the square wave geometry is seen to be ineffective at noise reduction for high frequencies.
2018-06-25T00:00:00ZAn affine model of the dynamics of astrophysical discsOgilvie, GIhttps://www.repository.cam.ac.uk/handle/1810/2789862023-12-21T08:03:28Z2018-01-01T00:00:00Zdc.title: An affine model of the dynamics of astrophysical discs
dc.contributor.author: Ogilvie, GI
dc.description.abstract: © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. Thin astrophysical discs are very often modelled using the equations of 2D hydrodynamics. We derive an extension of this model that describes more accurately the behaviour of a thin disc in the absence of self-gravity, magnetic fields, and complex internal motions. The ideal fluid theory is derived directly from Hamilton's Principle for a 3D fluid after making a specific approximation to the deformation gradient tensor. We express the equations in Eulerian form after projection on to a reference plane. The disc is thought of as a set of fluid columns, each of which is capable of a time-dependent affine transformation, consisting of a translation together with a linear transformation in three dimensions. Therefore, in addition to the usual 2D hydrodynamics in the reference plane, the theory allows for a deformation of the mid-plane (as occurs in warped discs) and for the internal shearing motions that accompany such deformations. It also allows for the vertical expansions driven in non-circular discs by a variation of the vertical gravitational field around the horizontal streamlines, or by a divergence of the horizontal velocity. The equations of the affine model embody conservation laws for energy and potential vorticity, even for non-planar discs.We verify that they reproduce exactly the linear theories of 3D warped and eccentric discs in a secular approximation. However, the affine model does not rely on any secular or small-amplitude assumptions and should be useful in more general circumstances.
2018-01-01T00:00:00ZA lower bound on the positive semidefinite rank of convex bodiesFawzi, HamzaDin, Mohab Safey Elhttps://www.repository.cam.ac.uk/handle/1810/2789802023-12-21T01:58:16Z2018-01-01T00:00:00Zdc.title: A lower bound on the positive semidefinite rank of convex bodies
dc.contributor.author: Fawzi, Hamza; Din, Mohab Safey El
dc.description.abstract: The positive semidefinite rank of a convex body $C$ is the size of its
smallest positive semidefinite formulation. We show that the positive
semidefinite rank of any convex body $C$ is at least $\sqrt{\log d}$ where $d$
is the smallest degree of a polynomial that vanishes on the boundary of the
polar of $C$. This improves on the existing bound which relies on results from
quantifier elimination. The proof relies on the B\'ezout bound applied to the
Karush-Kuhn-Tucker conditions of optimality. We discuss the connection with the
algebraic degree of semidefinite programming and show that the bound is tight
(up to constant factor) for random spectrahedra of suitable dimension.
2018-01-01T00:00:00ZRelativistic magnetised perturbations: Magnetic pressure versus magnetic tensionTseneklidou, DTsagas, CGBarrow, JDhttps://www.repository.cam.ac.uk/handle/1810/2788032023-12-21T03:04:02Z2018-01-01T00:00:00Zdc.title: Relativistic magnetised perturbations: Magnetic pressure versus magnetic tension
dc.contributor.author: Tseneklidou, D; Tsagas, CG; Barrow, JD
dc.description.abstract: We study the linear evolution of magnetised cosmological perturbations in the post-recombination epoch. Using full general relativity and adopting the ideal magnetohydrodynamic approximation, we refine and extend the previous treatments. More specifically, this is the first relativistic study that accounts for the effects of the magnetic tension, in addition to those of the field's pressure. Our solutions show that on sufficiently large scales, larger than the (purely magnetic) Jeans length, the perturbations evolve essentially unaffected by the magnetic presence. The magnetic pressure dominates on small scales, where it forces the perturbations to oscillate and decay. Close to the Jeans length, however, the field's tension takes over and leads to a weak growth of the inhomogeneities. These solutions clearly demonstrate the opposing action of the aforementioned two magnetic agents, namely of the field's pressure and tension, on the linear evolution of cosmological density perturbations.
2018-01-01T00:00:00ZGauge Mediation in the NMSSM with a Light Singlet: Sparticles within the
Reach of LHC Run IIAllanach, BenBadziak, MarcinHugonie, CyrilZiegler, Roberthttps://www.repository.cam.ac.uk/handle/1810/2787692023-12-21T08:46:09Z2015-10-12T00:00:00Zdc.title: Gauge Mediation in the NMSSM with a Light Singlet: Sparticles within the
Reach of LHC Run II
dc.contributor.author: Allanach, Ben; Badziak, Marcin; Hugonie, Cyril; Ziegler, Robert
dc.description.abstract: Relatively light stops in gauge mediation models are usually made compatible
with the Higgs mass of 125 GeV by introducing direct Higgs-messenger couplings.
We show that such couplings are not necessary in a simple and predictive model
that combines minimal gauge mediation and the next-to-minimal supersymmetric
standard model (NMSSM). We show that one can obtain a 125 GeV Standard
Model-like Higgs boson with stops as light as 1.1 TeV, thanks to the mixing of
the Higgs with a singlet state at ${\cal O}(90-100)$ GeV that can explain the
LEP excess. In this scenario the singlet-higgs-higgs superfields coupling
$\lambda$ is small and $\tan\beta$ large. Sparticle searches at the LHC may
come with additional $b-$jets or taus and may involve displaced vertices. The
sparticle production cross-section at the 13 TeV LHC can be ${\mathcal
O}(10-100)$ fb, leading to great prospects for discovery in the early phase of
LHC Run II.
2015-10-12T00:00:00ZInterpreting the CMS ℓ+ ℓ-jj+ missing transverse energy excess with a leptoquark modelAllanach, BAlves, AQueiroz, FSSinha, KStrumia, Ahttps://www.repository.cam.ac.uk/handle/1810/2787672023-12-21T09:11:50Z2015-01-01T00:00:00Zdc.title: Interpreting the CMS ℓ+ ℓ-jj+ missing transverse energy excess with a leptoquark model
dc.contributor.author: Allanach, B; Alves, A; Queiroz, FS; Sinha, K; Strumia, A
dc.description.abstract: Motivated by excesses in $ee jj$ and $e\nu jj$ channels observed by the CMS
collaboration, in 8 TeV LHC data, a model of lepto-quarks with mass around 500
GeV was proposed in the literature. In order to reproduce the claimed event
rate, lepto-quarks were assumed to have a significant partial branching ratio
into an extra sector, taken to be Dark Matter, other than the canonical $ej$.
We here show that the decay channel of lepto-quark into Dark Matter can fit
another excess claimed by CMS, in $\ell^+\ell^- jj E\!\!\!\!/_{\rm T}$: the
event rate, the distribution in di-lepton invariant mass and the rapidity range
are compatible with the data. We provide predictions for the forthcoming Run II
of the 14 TeV LHC and discuss aspects of dark matter detection.
2015-01-01T00:00:00ZZ′ models for the LHCb and g-2 muon anomaliesAllanach, BQueiroz, FSStrumia, ASun, Shttps://www.repository.cam.ac.uk/handle/1810/2787662023-12-21T08:20:02Z2016-01-01T00:00:00Zdc.title: Z′ models for the LHCb and g-2 muon anomalies
dc.contributor.author: Allanach, B; Queiroz, FS; Strumia, A; Sun, S
dc.description.abstract: We revisit a class of Z' explanations of the anomalies found by the LHCb
collaboration in $B$ decays, and show that the scenario is tightly constrained
by a combination of constraints: (i) LHC searches for di-muon resonances, (ii)
pertubativity of the Z' couplings; (iii) the $B_s$ mass difference, and (iv)
and electro-weak precision data. Solutions are found by suppressing the Z'
coupling to electrons and to light quarks and/or by allowing for a Z' decay
width into dark matter. We also present a simplified framework where a
TeV-scale Z' gauge boson that couples to standard leptons as well as to new
heavy vector-like leptons, can simultaneously accommodate the LHCb anomalies
and the muon g-2 anomaly.
2016-01-01T00:00:00ZWormhole throats in
<i>
R
<sup>m</sup>
</i>
gravityFurey, NDeBenedictis, Ahttps://www.repository.cam.ac.uk/handle/1810/2787382023-12-21T03:02:01Z2005-01-21T00:00:00Zdc.title: Wormhole throats in
<i>
R
<sup>m</sup>
</i>
gravity
dc.contributor.author: Furey, N; DeBenedictis, A
2005-01-21T00:00:00Z