291 research outputs found

    Cosmology with the Laser Interferometer Space Antenna

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    The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe

    Amplitudes for black holes

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    In recent years the double copy has provided a bridge between scattering amplitudes and gravitational interactions, allowing physicists to perform computations once unthinkable. Its strength relies on borrowing perturbative (much easier) results from gauge theories, and extracting classical results from quantum amplitudes. Recently, the gravitational two-body problem, central for the blooming field of gravitational wave physics, is being scrutinized under the light of such duality. In this thesis we work towards understanding how the double copy can help us compute classical gravity observables through the socalled “KMOC formalism”. This is a framework that has already received great interest from both the gravitational waves and the amplitude community, since it focuses directly on the computation of physical observables (for instance, without resorting to a Hamiltonian) allowing for a deeper understanding of underlying structures present in the classical limit of amplitudes

    Scattering Amplitudes in the Yang-Mills sector of Quantum Chromodynamics

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    We derive a new Minkowski space action for the pure gluonic sector of QCD that implements new interaction vertices local in the light-cone time with at least four legs and fixed helicities - the lowest vertex is the four-point MHV (Maximally Helicity Violating), higher point vertices include NkMHV\mathrm{N}^k \mathrm{MHV}, where 1 ⩜\leqslant k ⩜\leqslant n-4 and n is the number of external legs. The abscense of triple point interaction vertices makes it efficient in calculating higher multiplicity pure gluonic scattering amplitudes. This formulation is obtained via a canonical transformation of the light-cone Yang-Mills action, with the field transformations based on Wilson line functionals. At the quantum level, the action can only provide cut-constructible parts of amplitudes in 4D. In order to remedy that, we constructed the one-loop effective action starting with the Yang-Mills theory, which explicitly provides the missing contributions. This work provides a new field-theory action-based method to efficiently calculate higher multiplicity pure gluonic scattering amplitudes up to one loop.Comment: Thesis, 236 page

    Localizations with noncompact transverse spaces and covert symmetry breaking in supergravity

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    The focus of my doctoral work has been answering the question: Can lower-dimensional effective gravitational theories be found in a higher-dimensional theory with a non-compact transverse space? To answer this question this thesis is divided into two parts. First, I explore supergravity solutions on warped product manifolds and argue that they correspond to solutions of a modified Laplacian. I pay special attention to Type III † solutions, or solutions characterized by the presence of non-constant transverse zero modes, and emphasize that these are the only higher dimensional solutions corresponding to localized sources that yield effectively lower-dimensional physics when the transverse space has infinite volume. Second, I derive the lower dimensional effective field theory about such backgrounds. I discover that these effective field theories have covert symmetry breaking, spontaneous breaking of gauge symmetry which only appears at quartic order. I show this explicitly for D = d + 1 scalar electrodynamics with any boundary condition that corresponds to a non-constant transverse zero mode. The mathematical prerequisite for both of these conclusions is Sturm–Liouville theory with precise manipulations of Green’s formula. To support this I derive the fundamental conclusions of Sturm–Liouville theory for a restricted class of operator, that is the Laplacian, which relaxes some requirements for permissible boundary conditions of Sturm–Liouville theory. The answer to my focal question is: Yes; however, the lower-dimensional theory has novel corrections which were previously unexplored, and further research is indicated.Open Acces

    Path and Motion Planning for Autonomous Mobile 3D Printing

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    Autonomous robotic construction was envisioned as early as the ‘90s, and yet, con- struction sites today look much alike ones half a century ago. Meanwhile, highly automated and efficient fabrication methods like Additive Manufacturing, or 3D Printing, have seen great success in conventional production. However, existing efforts to transfer printing technology to construction applications mainly rely on manufacturing-like machines and fail to utilise the capabilities of modern robotics. This thesis considers using Mobile Manipulator robots to perform large-scale Additive Manufacturing tasks. Comprised of an articulated arm and a mobile base, Mobile Manipulators, are unique in their simultaneous mobility and agility, which enables printing-in-motion, or Mobile 3D Printing. This is a 3D printing modality, where a robot deposits material along larger-than-self trajectories while in motion. Despite profound potential advantages over existing static manufacturing-like large- scale printers, Mobile 3D printing is underexplored. Therefore, this thesis tack- les Mobile 3D printing-specific challenges and proposes path and motion planning methodologies that allow this printing modality to be realised. The work details the development of Task-Consistent Path Planning that solves the problem of find- ing a valid robot-base path needed to print larger-than-self trajectories. A motion planning and control strategy is then proposed, utilising the robot-base paths found to inform an optimisation-based whole-body motion controller. Several Mobile 3D Printing robot prototypes are built throughout this work, and the overall path and motion planning strategy proposed is holistically evaluated in a series of large-scale 3D printing experiments

    Moduli Stabilization in String Theory

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    We give an overview of moduli stabilization in compactifications of string theory. We summarize current methods for construction and analysis of vacua with stabilized moduli, and we describe applications to cosmology and particle physics. This is a contribution to the Handbook of Quantum Gravity.Comment: 74 pages. Invited chapter for the Handbook of Quantum Gravity (edited by Cosimo Bambi, Leonardo Modesto, and Ilya Shapiro, Springer 2023

    50 Years of quantum chromodynamics – Introduction and Review

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    Correlators on the Wilson Line Defect CFT

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    Konforme Feldtheorien (CFT) spielen eine SchlĂŒsselrolle in der modernen theoretischen Physik. Mit CFT beschreibt man reale physikalische Systeme bei KritikalitĂ€t. Dank der AdS/CFT-Korrespondenz spielt sie auch bei der Untersuchung der Quantengravitation eine zentrale Rolle. Auf der Seite der CFT steht die N=4 supersymmetrische Yang-Mills (SYM) Theorie. Diese Arbeit dreht sich hauptsĂ€chlich um die supersymmetrische Wilson-Linie und ihre Interpretation als konformer Defekt in N=4 SYM. Insbesondere konzentrieren wir uns auf Anregungen, die auf dem Defekt lokalisiert sind, sogenannte EinfĂŒgungen, deren Korrelatoren durch eine eindimensionale CFT beschrieben werden. Das erste Hauptergebnis dieser Arbeit ist ein effizienter Algorithmus zur Berechnung von Mehrpunkt Korrelationsfunktionen von SkalareinfĂŒgungen auf der Wilson-Linie bis zur nĂ€chsten Ordnung bei schwacher Kopplung kodieren. Es werden verschiedene Berechnungen solcher Vier-, FĂŒnf- und Sechspunkt-Korrelatoren gezeigt und ihre Eigenschaften diskutiert. DarĂŒber hinaus wird am Beispiel der Vierpunkt-Funktion die LeistungsfĂ€higkeit der Ward-IdentitĂ€ten veranschaulicht, die fĂŒr die Ableitung eines Ergebnisses nĂ€chster, vorletzter und fĂŒhrender Ordnung entscheidend sind. Dank dieser perturbativen Ergebnisse vermuten wir eine Mehrpunkt-Erweiterung der Ward-IdentitĂ€ten, die von den Vier-Punkt-Funktionen erfĂŒllt werden. Diese nichtperturbativen BeschrĂ€nkungen erweisen sich als fundamentale Bestandteile des Bootstraps einer FĂŒnfpunkt-Funktion bei starker Kopplung. Zum Abschluss dieser Arbeit definieren wir eine inhĂ€rent eindimensionale Mellin-Amplitude auf der nichtperturbativen Ebene mit geeigneten Subtraktionen und analytischen Fortsetzungen. Die Effizienz des 1d-Mellin-Formalismus zeigt sich auf der perturbativen Ebene. Man findet einen Ausdruck in geschlossener Form fĂŒr die Mellin-Transformation von Kontaktwechselwirkungen fĂŒhrender Ordnung, den man verwendet, um CFT-Daten zu extrahieren.Conformal field theory (CFT) plays a key role in modern theoretical physics. Through CFT we describe real physical systems at criticality and fixed points of the renormalization group flow. It is also central in the study of quantum gravity, thanks to the AdS/CFT correspondence. This thesis originates in the context of the N=4 supersymmetric Yang-Mills (SYM) theory, which represents the CFT side of this correspondence. This work mainly revolves around the supersymmetric Wilson line and its interpretation as a conformal defect in N=4 SYM. Particularly, we focus on excitations localized on the defect called insertions, whose correlators are described by a one-dimensional CFT. The first main result of this work is an efficient algorithm for computing multipoint correlation functions of scalar insertions on the Wilson line, consisting of recursion relations encoding the possible interactions up to next-to-leading order at weak coupling. We show various computations of such four-, five- and six-point correlators, and discuss their properties. Moreover, we use the four-point function case to illustrate the power of the Ward identities, which are crucial in deriving a next-to-next-to-leading order result. Thanks to these perturbative results, we find a family of differential operators annihilating our correlation functions, which we conjecture to be a multipoint extension of the Ward identities satisfied by the four-point functions. These non-perturbative constraints are shown to be fundamental ingredients in the bootstrap of a five-point function at strong coupling. To conclude this thesis, we define an inherently one-dimensional Mellin amplitude at the non-perturbative level with appropriate subtractions and analytical continuations. The efficiency of the 1d Mellin formalism is manifest at the perturbative level. We find a closed-form expression for the Mellin transform of leading order contact interactions and use it to extract CFT data

    Cosmology with the Laser Interferometer Space Antenna

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    ArtĂ­culo escrito por un elevado nĂșmero de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboraciĂłn, si lo hubiereThe Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universeThis work is partly supported by: A.G. Leventis Foundation; Academy of Finland Grants 328958 and 345070; Alexander S. Onassis Foundation, Scholarship ID: FZO 059-1/2018-2019; Amaldi Research Center funded by the MIUR program “Dipartimento di Eccellenza” (CUP: B81I18001170001); ASI Grants No. 2016-24-H.0 and No. 2016-24-H.1-2018; AtracciĂłn de Talento Grant 2019-T1/TIC-15784; AtracciĂłn de Talento contract no. 2019-T1/TIC-13177 granted by the Comunidad de Madrid; Ayuda ‘Beatriz Galindo Senior’ by the Spanish ‘Ministerio de Universidades’, Grant BG20/00228; Basque Government Grant (IT-979-16); Belgian Francqui Foundation; Centre national d’Etudes spatiales; Ben Gurion University Kreitman Fellowship, and the Israel Academy of Sciences and Humanities (IASH) & Council for Higher Education (CHE) Excellence Fellowship Program for International Postdoctoral Researchers; Centro de Excelencia Severo Ochoa Program SEV-2016-0597; CERCA program of the Generalitat de Catalunya; Cluster of Excellence “Precision Physics, Fundamental Interactions, and Structure of Matter” (PRISMA? EXC 2118/1); Comunidad de Madrid, Contrato de AtracciĂłn de Talento 2017-T1/TIC-5520; Czech Science Foundation GAČR, Grant No. 21-16583M; Delta ITP consortium; Department of Energy under Grant No. DE-SC0008541, DE-SC0009919 and DESC0019195; Deutsche Forschungsgemeinschaft (DFG), Project ID 438947057; Deutsche Forschungsgemeinschaft under Germany’s Excellence Strategy - EXC 2121 Quantum Universe - 390833306; European Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports (Project CoGraDS - CZ.02.1.01/0.0/0.0/15 003/0000437); European Union’s H2020 ERC Consolidator Grant “GRavity from Astrophysical to Microscopic Scales” (Grant No. GRAMS-815673); European Union’s H2020 ERC, Starting Grant Agreement No. DarkGRA-757480; European Union’s Horizon 2020 programme under the Marie Sklodowska-Curie Grant Agreement 860881 (ITN HIDDeN); European Union’s Horizon 2020 Research and Innovation Programme Grant No. 796961, “AxiBAU” (K.S.); European Union’s Horizon 2020 Research Council grant 724659 MassiveCosmo ERC-2016-COG; FCT through national funds (PTDC/FIS-PAR/31938/2017) and through project “BEYLA – BEYond LAmbda” with Ref. Number PTDC/FIS-AST/0054/2021; FEDER-Fundo Europeu de Desenvolvimento Regional through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI-01-0145- FEDER-031938) and research Grants UIDB/04434/2020 and UIDP/04434/2020; Fondation CFM pour la Recherche in France; Foundation for Education and European Culture in Greece; French ANR project MMUniverse (ANR-19-CE31-0020); FRIA Grant No.1.E.070.19F of the Belgian Fund for Research, F.R. S.-FNRS Fundação para a CiĂȘncia e a Tecnologia (FCT) through Contract No. DL 57/2016/CP1364/ CT0001; Fundação para a CiĂȘncia e a Tecnologia (FCT) through Grants UIDB/04434/2020, UIDP/04434/ 2020, PTDC/FIS-OUT/29048/2017, CERN/FIS-PAR/0037/2019 and “CosmoTests – Cosmological tests of gravity theories beyond General Relativity” CEECIND/00017/2018; Generalitat Valenciana Grant PROMETEO/2021/083; Grant No. 758792, project GEODESI; Government of Canada through the Department of Innovation, Science and Economic Development and Province of Ontario through the Ministry of Colleges and Universities; Grants-in-Aid for JSPS Overseas Research Fellow (No. 201960698); I?D Grant PID2020-118159GB-C41 of the Spanish Ministry of Science and Innovation; INFN iniziativa specifica TEONGRAV; Israel Science Foundation (Grant No. 2562/20); Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Nos. 20H01899 and 20H05853; IFT Centro de Excelencia Severo Ochoa Grant SEV-2; Kavli Foundation and its founder Fred Kavli; Minerva Foundation; Ministerio de Ciencia e Innovacion Grant PID2020-113644GB-I00; NASA Grant 80NSSC19K0318; NASA Hubble Fellowship grants No. HST-HF2-51452.001-A awarded by the Space Telescope Science Institute with NASA contract NAS5-26555; Netherlands Organisation for Science and Research (NWO) Grant Number 680-91-119; new faculty seed start-up grant of the Indian Institute of Science, Bangalore, the Core Research Grant CRG/2018/002200 of the Science and Engineering; NSF Grants PHY-1820675, PHY-2006645 and PHY-2011997; Polish National Science Center Grant 2018/31/D/ ST2/02048; Polish National Agency for Academic Exchange within the Polish Returns Programme under Agreement PPN/PPO/2020/1/00013/U/00001; PrĂł-Reitoria de Pesquisa of Universidade Federal de Minas Gerais (UFMG) under Grant No. 28359; RamĂłn y Cajal Fellowship contract RYC-2017-23493; Research Project PGC2018-094773-B-C32 [MINECO-FEDER]; Research Project PGC2018-094773-B-C32 [MINECO-FEDER]; ROMFORSK Grant Project. No. 302640; Royal Society Grant URF/R1/180009 and ERC StG 949572: SHADE; Shota Rustaveli National Science Foundation (SRNSF) of Georgia (Grant FR/18-1462); Simons Foundation/SFARI 560536; SNSF Ambizione grant; SNSF professorship Grant (No. 170547); Spanish MINECO’s “Centro de Excelencia Severo Ochoa” Programme Grants SEV-2016- 0597 and PID2019-110058GB-C22; Spanish Ministry MCIU/AEI/FEDER Grant (PGC2018-094626-BC21); Spanish Ministry of Science and Innovation (PID2020-115845GB-I00/AEI/10.13039/ 501100011033); Spanish Proyectos de I?D via Grant PGC2018-096646-A-I00; STFC Consolidated Grant ST/T000732/1; STFC Consolidated Grants ST/P000762/1 and ST/T000791/1; STFC Grant ST/ S000550/1; STFC Grant ST/T000813/1; STFC Grants ST/P000762/1 and ST/T000791/1; STFC under the research Grant ST/P000258/1; Swiss National Science Foundation (SNSF), project The Non-Gaussian Universe and Cosmological Symmetries, Project Number: 200020-178787; Swiss National Science Foundation Professorship Grants No. 170547 and No. 191957; SwissMap National Center for Competence in Research; “The Dark Universe: A Synergic Multi-messenger Approach” Number 2017X7X85K under the MIUR program PRIN 2017; UK Space Agency; UKSA Flagship Project, Eucli
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