Particle Physics

In this paper, I propose a general framework for understanding renormalization by drawing on the distinction between effective and continuum Quantum Field Theories (QFTs), and offer a comprehensive account of perturbative renormalization on this basis. My central claim is that the effective approach to renormalization provides a more physically perspicuous, conceptually coherent and widely applicable framework to construct perturbative QFTs than the continuum approach. I also show how a careful comparison between the two approaches: (i) helps to dispel the mystery (...) surrounding the success of the renormalization procedure; (ii) clarifies the various notions of renormalizability; and (iii) gives reasons to temper Butterfield and Bouatta's claim that some continuum QFTs are ripe for metaphysical inquiry (Butterfield & Bouatta, 2014). (shrink)

Large scale experiments at CERN’s Large Hadron Collider (LHC) rely heavily on computer simulations (CSs), a fact that has recently caught philosophers’ attention. CSs obviously require appropriate modeling, and it is a common assumption among philosophers that the relevant models can be ordered into hierarchical structures. Focusing on LHC’s ATLAS experiment, we will establish three central results here: (a) With some distinct modifications, individual components of ATLAS’ overall simulation infrastructure can be ordered into hierarchical structures. Hence, to a good degree (...) of approximation, hierarchical accounts remain valid at least as descriptive accounts of initial modeling steps. (b) In order to perform the epistemic function Winsberg (1999) assigns to models in simulation – generate knowledge through a sequence of skillful but non-deductive transformations – ATLAS’ simulation models have to be considered part of a network rather than a hierarchy, in turn making the associated simulation modeling messy rather than motley. Deriving knowledge-claims from this ‘mess’ requires two sources of justification: (i) holistic validation (also Lenhard and Winsberg, 2010, 2011), and (ii) model coherence. As it turns out, (c) the degree of model coherence sets HEP apart from other messy, simulation-intensive disciplines such as climate science, and the reasons for this are to be sought in the historical, empirical and theoretical foundations of the respective discipline. (shrink)

'Particle or Wave' explains the origins and development of modern physical concepts about matter and the controversies surrounding them.

Lakatos’s methodology of scientific research programmes centres around series of theories, with little regard to the role of models in theory construction. Modifying it to incorporate model-groups, clusters of developmental models that are intended to become new theories, provides a description of the model dynamics within the search for physics beyond the standard model. At the moment, there is no evidence for BSM physics, despite a concerted search effort especially focused around the standard model account of electroweak symmetry breaking. Using (...) the framework provided by Lakatosian research programmes, we can capture the way the periphery of a model-group changes as the available parameter space shrinks, while its central tenets remain untouched by unfavourable experimental findings. By way of motivation, I provide two case studies of model-groups that offer alternative mechanisms for electroweak symmetry breaking: supersymmetry and composite-Higgs models. Both of these model-groups are under pressure from the discovery of the Higgs boson, yet they have both been active research projects in the years after the Higgs discovery. However, a proper assessment of the progress of an ongoing research programme is impossible through a purely Lakatosian lens, so I propose replacing it with Laudan’s problem-solving account, which provides ongoing assessment, while offering normative guidance concerning the pursuit-worthiness of research programmes. My incorporation of model-groups into Lakatosian research programmes captures the developments of two attempts to expand our physical description of the world, and Laudan’s problem-solving rationality allows us to assess their pursuit-worthiness. (shrink)

There has been a growing trend to include non-causal models in accounts of scientific explanation. A worry addressed in this paper is that without a higher threshold for explanation there are no tools for distinguishing between models that provide genuine explanations and those that provide merely potential explanations. To remedy this, a condition is introduced that extends a veridicality requirement to models that are empirically underdetermined, highly-idealised, or otherwise non-causal. This condition is applied to models of electroweak symmetry breaking beyond (...) the Standard Model. (shrink)

The debate between Fraser and Wallace over the foundations of quantum field theory has spawned increased focus on both the axiomatic and conventional formalisms. The debate has set the tone for future foundational analysis, and has forced philosophers to “pick a side”. The two are seen as competing research programs, and the major divide between the two manifests in how each handles renormalization. In this paper I argue that the terms set by the Fraser-Wallace debate are misleading. AQFT and CQFT (...) should be viewed as complementary formalisms that start from the same physical basis. Further, the focus on cutoffs as demarcating the two approaches is also highly misleading. Though their methods differ, both axiomatic and conventional QFT seek to use the same physical principles to explain the same domain of phenomena. (shrink)

The cosmological constant problem is widely viewed as an important barrier and hint to merging quantum field theory and general relativity. It is a barrier insofar as it remains unsolved, and a solution may hint at a fuller theory of quantum gravity. I critically examine the arguments used to pose the cosmological constant problem, and find many of the steps poorly justified. In particular, there is little reason to accept an absolute zero point energy scale in quantum field theory, and (...) standard calculations are badly divergent. It is also unclear exactly how a semiclassical treatment of gravity would include a vacuum energy contribution to the total stress-energy. Large classes of solution strategies are also found to be conceptually wanting. I conclude that one should not accept the cosmological constant problem as standardly stated. (shrink)

Science is a process, through which theoretical frameworks are developed, new phenomena defined and discovered, and properties of entities tested. The goal of this dissertation is to illustrate how high-energy physics exemplified the process of theory construction from the 1950s to 1970s, and the promising ways in which it can continue to do so today. The lessons learned from the case studies examined here can inform future physics, and may provide methodological clues as to the best way forward today. I (...) examine the discovery of parity nonconservation in weak interactions, the emergence of Yang-Mills theories as the foundation of the standard model, and contemporary precision testing of quantum electrodynamics. In each of these cases, I examine the details of the physicists’ practice to draw conclusions regarding the epistemology behind successful episodes of theory construction. I reconstruct the methodology of each episode in order to find generalizable lessons to apply to contemporary issues at the frontiers of the search for a theory of quantum gravity. In order to understand the many moving parts in each case study, I introduce a new terminology to distinguish the “parts” of a scientific discipline, inspired by the literature on scientific modelling. These terms—theoretical framework, dynamical model, phenomenological model, experiment, and mathematical tools—are meant to aid in investigating other quantitative scientific disciplines beyond high-energy physics. Ultimately, high-energy physics is at its best when various avenues of theoretical ideas are being pursued, spurring the development of new mathematical techniques to use as tools, and new ideas are quickly and vigorously tested experimentally. Proliferation of new ideas in response to theoretical developments is characteristic of the era of construction of the standard model, and is still ongoing in precision testing of quantum electrodynamics today. (shrink)

In this paper I detail three major mathematical developments that led to the emergence of Yang–Mills theories as the foundation for the standard model of particle physics. In less than 10 years, work on renormalizability, the renormalization group, and lattice quantum field theory highlighted the utility of Yang–Mills type models of quantum field theory by connecting poorly understood candidate dynamical models to emerging experimental results. I use this historical case study to provide lessons for theory construction in physics, and touch (...) on issues related to renormalization group realism from a more historical perspective. In particular, I highlight the fact that much of the hard work in theory construction comes when trying to understand the consequences and representational capacities of a theoretical framework. (shrink)

I defend an analog of probabilism that characterizes rationally coherent estimates for chances. Specifically, I demonstrate the following accuracy-dominance result for stochastic theories in the C*-algebraic framework: supposing an assignment of chance values is possible if and only if it is given by a pure state on a given algebra, your estimates for chances avoid accuracy-dominance if and only if they are given by a state on that algebra. When your estimates avoid accuracy-dominance (roughly: when you cannot guarantee that other (...) estimates would be more accurate), I say that they are sufficiently coherent. In formal epistemology and quantum foundations, the notion of rational coherence that gets more attention requires that you never allow for a sure loss (or “Dutch book”) in a given sort of betting game; I call this notion full coherence. I characterize when these two notions of rational coherence align, and I show that there is a quantum state giving estimates that are sufficiently coherent, but not fully coherent. (shrink)

According to the Standard Model of particle physics, some gauge transformations are physical symmetries. That is, they are mathematical transformations that relate representatives of distinct physical states of affairs. This is at odds with the standard philosophical position according to which gauge transformations are an eliminable redundancy in a gauge theory's representational framework. In this paper I defend the Standard Model's treatment of gauge from an objection due to Richard Healey. If we follow the Standard Model in taking some gauge (...) transformations to be physical symmetries then we face the “strong CP problem”, but if we adopt the standard philosophical position on gauge then the strong CP problem dissolves. Healey offers this as a reason in favor of the standard philosophical view. However, as I argue here, following Healey's recommendation gives a theory that makes bad empirical predictions. (shrink)

contents -/- i. the atom's brisance is defensive, perhaps ii. particle and Physicist iterate the other iii. Bohm was like the wave function iv. the quest for Quantum Gravity, for Unity v. action is action at a distance vi. think a simple Fractal vii. the world is flat viii. Sun is at the center.

Nature seems to be such that we can describe it accurately with quantum theories of bosons and fermions alone, without resort to parastatistics. This has been seen as a deep mystery: paraparticles make perfect physical sense, so why don’t we see them in nature? We consider one potential answer: every paraparticle theory is physically equivalent to some theory of bosons or fermions, making the absence of paraparticles in our theories a matter of convention rather than a mysterious empirical discovery. We (...) argue that this equivalence thesis holds in all physically admissible quantum field theories falling under the domain of the rigorous Doplicher–Haag–Roberts approach to superselection rules. Inadmissible parastatistical theories are ruled out by a locality-inspired principle we call charge recombination. 1 Introduction2 Paraparticles in Quantum Theory3 Theoretical Equivalence3.1 Field systems in algebraic quantum field theory3.2 Equivalence of field systems4 A Brief History of the Equivalence Thesis4.1 The Green decomposition4.2 Klein transformations4.3 The argument of Drühl, Haag, and Roberts4.4 The Doplicher–Roberts reconstruction theorem5 Sharpening the Thesis6 Discussion6.1 Interpretations of Quantum Mechanics6.2 Structuralism and haecceities6.3 Paraquark theories. (shrink)

Our paper studies the anatomy of the discovery of the Higgs boson at the Large Hadron Collider and its influence on the broader model landscape of particle physics. We investigate the phases of this discovery, which led to a crucial reconfiguration of the model landscape of elementary particle physics and eventually to a confirmation of the standard model. A keyword search of preprints covering the electroweak symmetry breaking sector of particle physics, along with an examination of physicists own understanding of (...) the discovery as documented in semiannual conferences, has allowed us an empirical investigation of its model dynamics. From our analyses we draw two main philosophical lessons concerning the nature of scientific reasoning in a complex experimental and theoretical environment. For one, from a confirmation standpoint, some SM alternatives could be considered even more confirmed by the Higgs discovery than the SM. Nevertheless, the SM largely remains the commonly accepted account of EWSB. We present criteria for comparing degrees of confirmation and expose some limits of a purely logical approach to understanding the Higgs discovery as a victory for the SM. Second, we understand the persistence of SM alternatives in the face of disfavourable evidence by borrowing the Lakatosian concept of a research programme, where the core idea behind a group of models survives, while other aspects adapt to incoming data. In order to apply this framework to the model landscape of EWSB, we must introduce a new category of research programme, the model-group, and we test its viability using the example of composite Higgs models. (shrink)

Cartea abordează bazele fenomenlogice din fizica atomică, fizica nucleară, radioactivitatea, fizica particulelor, fisiunea, fuziunea și energia nucleară. Conținutul oferă o perspectivă modernă a domeniului, simultan cu o retrospectivă istorică a dezvoltării sale. Fiecare capitol pune accent pe explicațiile fizice ale fenomenelor, ocurența naturală, măsurare, și utilizarea practică a fenomenelor respective. -/- CUPRINS: -/- Fizica atomică - Natura atomică a materiei - - Ipoteze atomice - - Proprietățile atomilor - - - Proprietăți nucleare - - - Masa - - - Forma (...) și dimensiunea - - - Dezintegrarea radioactivă - - - Momentul magnetic - - - Nivelurile energetice - - - Valența și comportamentul legăturilor - - - Stări - - Imagistica atomică - - Structura atomului - - - Particule subatomice - - - Nucleul - - - Norul de electroni Atomul și cuanta - Descoperirea nucleului atomic - Descoperirea electronului - - Descoperirea - Spectroscopia atomică - Linii spectrale - - Teorie - - Atomii - - Linii spectrale - - - Tipuri de spectre de linii - Modelul Bohr al atomului - - Origine - - Mărimea relativă a atomilor (Raza atomilor) - - - Definiții - - - Raze atomice măsurată empiric - - - Raze atomice calculate - - Nivele energetice cuantificate: Undele electronilor (Nivele energetice) - - - Explicație - - - Tranziții ale nivelelor de energie - Mecanica cuantică - - Istorie - - Formulări matematice - Principiul corespondenței - - Mecanica cuantică Nucleul atomic și radioactivitatea - Razele X - - Istorie - - Proprietăți - - - Interacțiunea cu materia - - Producere - - - Detectoare - - - Utilizări medicale - Radiații alfa, beta și gama - Radiații ionizante - - Radiația alfa - - - Utilizări - - Radiația beta - - - Utilizări - - Radiația gama - - - Utilizări - Nucleul atomic - - Structura nucleară - - Compoziție și formă - - Forțe - - - Forța nucleară slabă - - - Forța nucleară tare - Izotopi - - Izotop vs. nuclid - - Definiția - - Notație - - Izotopi radioactivi, primordiali și stabili - Dezintegrarea radioactivă - - Baza teoretică a fenomenelor de dezintegrare - - Apariție și aplicații - - Originea nuclizilor radioactivi - Timpul de înjumătățire - - Detectoare de radiații (Detectoare de particule) - - Detectoare de ionizare gazoasă - - Detector de urme nucleare în stare solidă - - Calorimetre - - Detectoare plate cu microcanale - - Detectarea neutronilor - - Detectoare moderne - - - Detector ermetic - - Instrumente de protecție împotriva radiațiilor - - - Instrumente instalate - - - Instrumente portabile - - Detectoare de particule în cercetare - Transmutarea elementelor (Transmutarea nucleară) - - Istorie - - - Alchimie - - - Fizica modernă - - Transmutarea naturală (Transmutarea în univers) - - Transmutarea artificială (Transmutarea deșeurilor nucleare) - - - Tipurile de reactoare - - - Tipuri de combustibil - - - Motivația din spatele transmutării - - - Produse de fisiune cu durată lungă de viață - Izotopi radioactivi (Radionuclizi) - - Origine - - - Natural - - - Fisiunea nucleară - - - Sintetic - - Utilizări - Datarea radiometrică - - Bazele datării radiometrice - - - Dezintegrarea radioactivă - - - Precizia datării radiometrice - - - Temperatura de închidere - - - Ecuația vârstei - - Datarea cu carbon - - - Detaliile fizice și chimice - - - Principii - - - Considerații privind datarea - - Datarea cu uraniu - - - Metoda de datare cu uraniu-plumb - - - Metoda de datare cu uraniu-toriu - Efectele radiațiilor asupra oamenilor - - Efectele asupra sănătății - - Expunerea la radiații - - - Expunerea profesională - - - Expunerea publica - - - Zborul în spațiu - - - Transportul aerian - - - Semne de avertizare privind pericolele de radiație - - Dozarea radiațiilor - - - Măsurare Fizica particulelor - Istoria - Modelul Standard - Fizica particulelor experimentală - Obiecții - Politici publice - Particule elementare - - Particule elementare - - - Fermioni - - - - Cuarci - - - Cuarci - - - - Leptoni - - - Leptoni - - - Bosoni - - - Particule ipotetice - - Particule compuse - - - Hadroni - - - Barioni - - - Mezoni - - - Nuclee atomice - - - Atomi - - - Molecule - - Substanțe condensate - - Alte particule - - Extensii ale Modelului Standard - - - Marea unificare - - - Supersimetria - - - Teoria corzilor - - - Teoria preonilor - Protoni - Neutroni - - Istoric - - - Evoluția actuală - Electron - - Clasificare - - Proprietăți fundamentale - Cuarci - Fotoni - Gluoni - Bosoni W și Z - - Bosonul Higgs - Neutrino - - Neutrino, noul sistem de comunicații - - Telefonul – particulă - - Comunicații cu submarinele - - Mesaje pentru călătoria în timp - Fizica acceleratorilor - - Accelerarea și interacțiunea particulelor cu structuri RF - - Dinamica fluxului - - Coduri de modelare - - Diagnosticările fluxului - - Toleranțele mașinii Fisiunea și fuziunea nucleară - Istorie - - Descoperirea nucleului - - Descoperirea neutronului - - Câmpul bozonic - - Mezoni - Fisiunea nucleară - - Mecanismul - - Reactoare de fisiune nucleară - - - Mecanism - - - - Fisiunea - - - - Generarea de căldură - - - - Răcirea - - - - Controlul reactivității - - - - Generarea de energie electrică - - Reactoare nucleare cu apă grea presurizată - CANDU - - - Scopul utilizării apei grele - - - Avantaje și dezavantaje - - - Emisiile de tritiu - - - Reactorul CANDU - - - Centrala Nucleară de la Cernavodă - - - - Reactoarele - - - - Incidente - - Plutoniu - - - Proprietăți fizice - - Reactoare nucleare reproducătoare - - - Eficiența combustibilului și tipurile de deșeuri nucleare - - - Raportul de conversie, pragul de rentabilitatea, raportul de reproducere, timpul de dublare și arderea - - - Tipuri de reactoare reproducătoare - - Energia de fisiune - - - Centrale nucleare - - - Probleme de mediu - - - Energia nucleară în România - - Echivalența masă-energie în reacțiile nucleare - - - Istorie - - - Exemplu practic - - - Eficiența - Fuziunea nucleară - - Procesul - - Controlul fuziunii (Energia de fuziune) - - - Descriere - - - - Mecanism - - - - Secțiunea transversală - - - - Criteriul Lawson - - - - Produs triplu: densitate, temperatură, timp - - - - Comportamentul plasmei - - - - Captarea energiei Probleme nerezolvate - Fizica nucleară - Fizica particulelor / Fizica energiilor înalte Referințe Despre autor - Nicolae Sfetcu - - De același autor - - Contact Editura - MultiMedia Publishing . 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The paper is concerned with explaining some of the principal theoretical developments in elementary particle physics and discussing the associated methodological problems both in respect of heuristics and appraisal. Particular reference is made to relativistic quantum field theory, renormalization, Feynman diagram techniques, the analytic S-matrix and the Chew — Frautschi bootstrap.

Die Frage der Erhaltung der Parität bei der Wechselwirkung von Elementarteilchen, der Vorschlag ihrer Verletzung, die experimentelle Bestätigung dieses Vorschlags und die daraus sich ergebenden Folgerungen, die zur Formulierung der mathematischen Struktur der schwachen Wechselwirkungen führten, sind die wichtigsten Entwicklungen in der Elementarteilchenphysik während der Periode von 1953 bis 1958. Vorliegender Aufsatz versucht die rationale Rekonstruktion dieser Periode und des Forschungsprogrammes, welches als eines der progressivsten Programme der modernen Physik angesehen wird. Hierzu benutzen wir eine modifizierte Fassung von Poppers tetradischem (...) Schema als auch die Bemerkungen von Lakatos über gewisse Aspekte der Methodologie von Forschungsprogrammen. Es wird unterstrichen, daß die Dynamik der positiven Heuristik derart war, daß die theoretische Forschung fortgeführt werden konnte, trotz experimenteller Resultate, die nur als Gegenbeweise gegen die vorgeschlagene Struktur der schwachen Wechselwirkungen angesehen werden konnten. (shrink)

Summary Some case studies in elementary particle physics are presented in this work, that can be used for the critical appraisal of specific criteria which were proposed to account for the development of Heisenberg's work. It is attempted to define the philosophical problems associated with and emerging from the structures of theories, rather than analyse the philosophical aspects of concepts used in elementary particle physics. This necessitates the discussion of the relationship between theory and experiment, and the role of the (...) mathematical framework being used. The question of elementarity is studied in this connection. Popper's tetradic schema and his concept of world three are modified, and it is shown that the new schema can accommodate the development of certain research programs in a much more satisfactory manner. As a result of the systematic treatment of specific research programs, the principle of contextual re-interpretation is expanded by specifying the different kinds of interpretations at the various stages of development of theories. It is also shown that principles such as those of simplicity and beauty can be understood in terms of the mathematical structure of the theories, and their methodological importance is emphasized. (shrink)

We present the idea of searching for X-rays as a signature of the mechanism inducing the spontaneous collapse of the wave function. Such a signal is predicted by the continuous spontaneous localization theories, which are solving the “measurement problem” by modifying the Schrödinger equation. We will show some encouraging preliminary results and discuss future plans and strategy.

This is an introduction to renormalization group methods in quantum field theory aimed at philosophers of science. review path integral methods, the relationship between early renormalization theory and renormalization group methods, and conceptual shifts in thinking about quantum field theory spurred by the development of renormalization group methods.

My aim in this paper is twofold: to distinguish two notions of naturalness employed in beyond the standard model physics and to argue that recognizing this distinction has methodological consequences. One notion of naturalness is an “autonomy of scales” requirement: it prohibits sensitive dependence of an effective field theory’s low-energy observables on precise specification of the theory’s description of cutoff-scale physics. I will argue that considerations from the general structure of effective field theory provide justification for the role this notion (...) of naturalness has played in BSM model construction. A second, distinct notion construes naturalness as a statistical principle requiring that the values of the parameters in an effective field theory be “likely” given some appropriately chosen measure on some appropriately circumscribed space of models. I argue that these two notions are historically and conceptually related but are motivated by distinct theoretical considerations and admit of distinct kinds of solution. (shrink)

Four initial postulates are presented (with two more added later), which state that construction of the physical universe proceeds from a sequence of discrete steps or "projections" --- a process that yields a sequence of discrete levels (labeled 0, 1, 2, 3, 4). At or above level 2 the model yields a (3+1)-dimensional structure, which is interpreted as ordinary space and time. As a result, time does not exist below level 2 of the system, and thus the quantum of action, (...) h, which depends on time (since its unit is time•energy), also does not exist below level 2. This implies that the quantum of action is not fundamental, and thus e.g. that the physical universe cannot have originated from a quantum fluctuation. When the gravitational interaction for the model is developed, it is seen that the basic ingredient for gravity is already operating at level 1 of the system, which implies that gravity, too, is not fundamentally quantum mechanical (since, as stated, h only kicks in at level 2) --- perhaps obviating the need for a quantum theory of gravity. Further arguments along this line lead to the conclusion that quantum fluctuations cannot be a source of gravity, and thus cannot contribute to the cosmological constant --- thereby averting the cosmological constant problem. Along the way, the model also provides explanations for dark energy, the beginning and ending of inflation, quark confinement, and more. Although the model dethrones the quantum, it nevertheless elevates an idea in physics that was engendered by quantum mechanics: the necessary role of "observers" in constructing the world. (shrink)

The recent discovery of the Higgs at 125 GeV by the ATLAS and CMS experiments at the LHC has put significant pressure on a principle which has guided much theorizing in high energy physics over the last 40 years, the principle of naturalness. In this paper, I provide an explication of the conceptual foundations and physical significance of the naturalness principle. I argue that the naturalness principle is well-grounded both empirically and in the theoretical structure of effective field theories, and (...) that it was reasonable for physicists to endorse it. Its possible failure to be realized in nature, as suggested by recent LHC data, thus represents an empirical challenge to certain foundational aspects of our understanding of QFT. In particular, I argue that its failure would undermine one class of recent proposals which claim that QFT provides us with a picture of the world as being structured into quasi-autonomous physical domains. (shrink)

Following the 26th General Conference on Weights and Measures are fixed the numerical values of the 4 physical constants ($h, c, e, k_B$). This is premised on the independence of these constants. This article discusses a model of a mathematical electron from which can be defined the Planck units as geometrical objects (mass M=1, time T=2$\pi$ ...). In this model these objects are interrelated via this electron geometry such that once we have assigned values to 2 Planck units then we (...) have fixed the values for all Planck units. As all constants can then be defined using geometrical forms (in terms of 2 fixed mathematical constants, 2 unit-specific scalars and a defined relationship between the units $kg, m, s, A$), the least precise CODATA 2014 constants ($G, h, e, m_e, k_B$...) can then be solved via the most precise ($c, \mu_0, \alpha, R_\infty$), with numerical precision limited by the precision of the fine structure constant $\alpha$. In terms of this model we now for example have 2 separate values for elementary charge, calculated from ($c, \alpha, R_\infty$) and the 2017 revision. (shrink)

This chapter (in French) compares the ways to access to events in science and in art. In particular, the Déotte's concept of "appareil" is discussed. To be published in Jean-Louis Déotte and Sylvestra Mariniello (ed.), Appareil et Intermédialité, L'Harmattan, 2007.

Recent discussions of emergence in physics have focussed on the use of limiting relations, and often particularly on singular or asymptotic limits. We discuss a putative example of emergence that does not fit into this narrative: the case of phonons. These quasi-particles have some claim to be emergent, not least because the way in which they relate to the underlying crystal is almost precisely analogous to the way in which quantum particles relate to the underlying quantum field theory. But there (...) is no need to take a limit when moving from a crystal lattice based description to the phonon description. Not only does this demonstrate that we can have emergence without limits, but also provides a way of understanding cases that do involve limits. (shrink)

Symmetries have a crucial role in today’s physics. In this thesis, we are mostly concerned with time reversal invariance (T-symmetry). A physical system is time reversal invariant if its underlying laws are not sensitive to the direction of time. There are various accounts of time reversal transformation resulting in different views on whether or not a given theory in physics is time reversal invariant. With a focus on quantum mechanics, I describe the standard account of time reversal and compare it (...) with my alternative account, arguing why it deserves serious attention. Then, I review three known ways to T-violation in quantum mechanics, and explain two unique experiments made to detect it in the neutral K and B mesons. (shrink)

The different interpretations of quark mixing involved in weak interaction processes in the Standard Model and the Generation Model are discussed with a view to obtaining a physical understanding of the Cabibbo angle and related quantities. It is proposed that hadrons are composed of mixed-quark states, with the quark mixing parameters being determined by the Cabibbo-Kobayashi-Maskawa matrix elements. In this model, protons and neutrons contain a contribution of about 5% and 10%, respectively, of strange valency quarks.

This thesis is a work of experimental physics, a search for new physics with the ATLAS experiment. I post this thesis on the PhilArchive because it includes a pedagogical summary of quantum mechanics and the standard model of particle physics in the combination of chapters 1-2 and appendix A. This was my attempt at the end of my PhD of giving a bird's eye view of the standard model, with a thorough bibliography of the publication trail that lead to its (...) development. I find myself pointing to it at philosophy conferences. // -/- This thesis presents a review of work on the performance of the reconstruction and identification of hadronic tau decays and studies of events reconstructed with a ditau final state with the ATLAS detector at the Large Hadron Collider. The first cut-based tau identification used with ATLAS data and the first observations of W→τν and Z→ττ at ATLAS are described, as well as many of the issues concerning the calibration and systematic uncertainties of reconstructed taus. The first measurement of the Z→ττ cross section at ATLAS with 2010 dataset is reviewed. Last, results are presented from the first search for high-mass resonances decaying to ττ at ATLAS with the 2011 dataset. (shrink)

We introduce a novel point of view on the “models as mediators” framework in order to emphasize certain important epistemological questions about models in science which have so far been little investigated. To illustrate how this perspective can help answer these kinds of questions, we explore the use of simplified models in high energy physics research beyond the Standard Model. We show in detail how the construction of simplified models is grounded in the need to mitigate pressing epistemic problems concerning (...) the uncertainty inherent in the present theoretical and experimental contexts. (shrink)

Fundamental physics contains an important link between properties of elementary particles and continuous symmetries of particle systems. For example, properties such as mass and spin are said to be 'associated' with specific continuous symmetries. -/- These 'associations' have played a key role in the discovery of various new particle kinds, but more importantly: they are thought to provide a deep insight into the nature of physical reality. The link between properties and symmetries has been said to call for a radical (...) revision of perceived metaphysical orthodoxy. However, if we are to use claims about an 'association' between properties and symmetries in the articulation of metaphysical views, we first need to develop a sufficiently precise understanding of the content of these claims. The goal of this paper is to do just that. (shrink)

Atomistic metaphysics motivated an explanatory strategy which science has pursued with great success since the scientific revolution. By decomposing matter into its atomic and subatomic parts physics gave us powerful explanations and accurate predictions as well as providing a unifying framework for the rest of science. The success of the decompositional strategy has encouraged a widespread conviction that the physical world forms a compositional hierarchy that physics and other sciences are progressively articulating. But this conviction does not stand up to (...) a closer examination of how physics has treated composition, as a variety of case studies will show. (shrink)

In Bohmian mechanics elementary particles exist objectively, as point particles moving according to a law determined by a wavefunction. In this context, questions as to whether the particles of a certain species are real---questions such as, Do photons exist? Electrons? Or just the quarks?---have a clear meaning. We explain that, whatever the answer, there is a corresponding Bohm-type theory, and no experiment can ever decide between these theories. Another question that has a clear meaning is whether particles are intrinsically distinguishable, (...) i.e., whether particle world lines have labels indicating the species. We discuss the intriguing possibility that the answer is no, and particles are points---just points. (shrink)

The concept of mass is one of the most fundamental notions in physics, comparable in importance only to those of space and time. But in contrast to the latter, which are the subject of innumerable physical and philosophical studies, the concept of mass has been but rarely investigated. Here Max Jammer, a leading philosopher and historian of physics, provides a concise but comprehensive, coherent, and self-contained study of the concept of mass as it is defined, interpreted, and applied in contemporary (...) physics and as it is critically examined in the modern philosophy of science. With its focus on theories proposed after the mid-1950s, the book is the first of its kind, covering the most recent experimental and theoretical investigations into the nature of mass and its role in modern physics, from the realm of elementary particles to the cosmology of galaxies.The book begins with an analysis of the persistent difficulties of defining inertial mass in a noncircular manner and discusses the related question of whether mass is an observational or a theoretical concept. It then studies the notion of mass in special relativity and the delicate problem of whether the relativistic rest mass is the only legitimate notion of mass and whether it is identical with the classical mass. This is followed by a critical analysis of the different derivations of the famous mass-energy relationship E = mc2 and its conflicting interpretations. Jammer then devotes a chapter to the distinction between inertial and gravitational mass and to the various versions of the so-called equivalence principle with which Newton initiated his Principia but which also became the starting point of Einstein's general relativity, which supersedes Newtonian physics. The book concludes with a presentation of recently proposed global and local dynamical theories of the origin and nature of mass.Destined to become a much-consulted reference for philosophers and physicists, this book is also written for the nonprofessional general reader interested in the foundations of physics. (shrink)

In the absence of new physics around \ GeV, the electroweak vacuum is at best metastable. This represents a major challenge for high scale inflationary models as, during the early rapid expansion of the universe, it seems difficult to understand how the Higgs vacuum would not decay to the true lower vacuum of the theory with catastrophic consequences if inflation took place at a scale above \ GeV. In this paper we show that the non-minimal coupling of the Higgs boson (...) to curvature could solve this problem by generating a direct coupling of the Higgs boson to the inflationary potential thereby stabilizing the electroweak vacuum. For specific values of the Higgs field initial condition and of its non-minimal coupling, inflation can drive the Higgs field to the electroweak vacuum quickly during inflation. (shrink)

In the author’s previous contribution to this journal (Rosen 2015), a phenomenological string theory was proposed based on qualitative topology and hypercomplex numbers. The current paper takes this further by delving into the ancient Chinese origin of phenomenological string theory. First, we discover a connection between the Klein bottle, which is crucial to the theory, and the Ho-t’u, a Chinese number archetype central to Taoist cosmology. The two structures are seen to mirror each other in expressing the psychophysical (phenomenological) action (...) pattern at the heart of microphysics. But tackling the question of quantum gravity requires that a whole family of topological dimensions be brought into play. What we find in engaging with these structures is a closely related family of Taoist forebears that, in concert with their successors, provide a blueprint for cosmic evolution. Whereas conventional string theory accounts for the generation of nature’s fundamental forces via a notion of symmetry breaking that is essentially static and thus unable to explain cosmogony successfully, phenomenological/Taoist string theory entails the dialectical interplay of symmetry and asymmetry inherent in the principle of synsymmetry. This dynamic concept of cosmic change is elaborated on in the three concluding sections of the paper. Here, a detailed analysis of cosmogony is offered, first in terms of the theory of dimensional development and its Taoist (yin-yang) counterpart, then in terms of the evolution of the elemental force particles through cycles of expansion and contraction in a spiraling universe. The paper closes by considering the role of the analyst per se in the further evolution of the cosmos. (shrink)

Three separate articles make up the chapters of this dissertation. They were written with different aims and audiences in mind, but each deals in some way with one or more "principles" that have been invoked in argumentation and explanation in the physical sciences. The principles of concern are propositions which have an "aesthetic" or "foundational" or "philosophical" character and which are generally believed to be widely applicable or particularly powerful--for example, the Principle of Plenitude, the Principle of Mathematical Beauty, Occam's (...) Razor, the Cosmological Principle, and the Copernican Principle. ;Chapter 1 provides an overview of the nature and uses of principles in scientific reasoning and examines in some detail the use of the Principle of Plenitude in the introduction of "tachyons" into theoretical physics during the 1960s. Chapter 2 is a short biography of P. A. M. Dirac , one of the founders of quantum mechanics, who believed that the Principle of Mathematical Beauty should serve as physicists' guide to truth. Chapter 3 traces the history of the idea of faster-than-light particles in physics since the late 1800s; this idea matured with the rise of the subfield of tachyon physics in the 1960s, and physicists appealed to the Principle of Plenitude to argue for the existence of the particles, which are still only hypothetical. ;According to the thesis developed in these chapters, the epistemological status of principles has evolved over the history of science. While they were once hallowed as a priori truths, in modern science they have increasingly been employed critically, in light of the results of scientific inquiry. That is, science has moved toward making principles testable, subject to rejection or revision, on a par with other scientific propositions. (shrink)

Several works in the last few years devoted to measure fundamental probes of contemporary cosmology have suggested the existence of a delocalized dominant component , in addition to the several-decade-old evidence for “dark matter” other than ordinary baryons, both assuming the description of gravity to be correct. Either we are faced to accept the ignorance of at least 95 % of the content of the universe or consider a deep change of the conceptual framework to understand the data. Thus, the (...) situation seems to be completely favorable for a Kuhnian paradigm shiftin either particle physics or cosmology. We attempt to offer here a brief discussion of these issues from this particular perspective, arguing that the situation qualifies as a textbook Kuhnian anomaly, and offer a tentative identification of some of the actual elements typically associated with the paradigm shift process “in the works” in contemporary science. (shrink)