arXiv subjects

Richard Dawid

Publications and source records attributed to Richard Dawid.

11 recordsLinked to original sources

arXiv2025

Realism and Ontology in Quantum Mechanics and String Theory

Dualities in physics have challenged traditional forms of scientific realism by undermining the idea that theories describe a unique underlying ontology. In this paper, we develop a new perspective on scientific realism that responds to this challenge. We argue that while realist commitment remains appropriate at the level of a theory's full formal structure, ontological commitment should be treated as tied to specific empirical contexts rather than to a fixed, real ontology. Our proposal draws inspiration from Dennett's notion of a "compression algorithm" as a defining criterion of a scientific theory. On this basis, we separate realism from ontological commitment. To clarify the stakes of this distinction, we contrast our approach with common core realism, which locates ontology in the invariant structure shared by dual models. Focusing on dualities in quantum mechanics and string theory, we show how our view accommodates ontological pluralism while preserving a robust form of structural realism.

physics.hist-ph↗

arXiv2025

Decoherence and Probability

One cannot justifiably presuppose the physical salience of structures derived via decoherence theory based upon an entirely uninterpreted use of the quantum formalism. Non-probabilistic accounts of the emergence of probability via decoherence are unconvincing. An alternative account of the emergence of probability involves the combination of a partially interpreted decoherence model and an averaging of observables with respect to a positive-definite quasi-probability function and neglect of terms $O(\hbar)$. Our analysis delimits the context in which the combination of decoherence and a semi-classical averaging allows us to recover a classical probability model within an emergent coarse-grained description.

quant-ph↗

arXiv2024

A Bayesian Model of Credence in Low Energy Supersymmetry

We carry out a quantitative Bayesian analysis of the evolution of credences in low energy supersymmetry (SUSY) in light of the most relevant empirical data. The analysis is based on the assumption that observers apply principles of optimism or pessimism about theory building in a coherent way. On this basis, we provide a rough assessment of the current range of plausible credences in low energy SUSY and determine in which way LHC data changes those credences. For observers who had been optimistic about low energy SUSY before the LHC, the method reports that LHC data does lead to decreased credences in accordance with intuition. The decrease is moderate, however, and keeps posteriors at very substantial levels. The analysis further establishes that a very high but not yet indefensible degree of pessimism regarding the success chances of theory building still results in quite significant credences in GUT and low energy SUSY for the time right before the start of the LHC. The pessimist's credence in low energy SUSY remains nearly unchanged once LHC data is taken into account.

physics.hist-ph↗

arXiv2018

Chronic Incompleteness, Final Theory Claims, and the Lack of Free Parameters in String Theory

String theory has not even come close to a complete formulation after half a century of intense research. On the other hand, a number of features of the theory suggest that the theory, once completed, may be a final theory. It is argued in this chapter that those two conspicuous characteristics of string physics are related to each other. What links them together is the fact that string theory has no dimensionless free parameters at a fundamental level. The paper analyses possible implications of this situation for the long term prospects of theory building in fundamental physics.

physics.hist-ph↗

arXiv2018

On the Empirical Consequences of the AdS/CFT Duality

We provide an analysis of the empirical consequences of the AdS/CFT duality with reference to the application of the duality in a fundamental theory, effective theory and instrumental context. Analysis of the first two contexts is intended to serve as a guide to the potential empirical and ontological status of gauge/gravity dualities as descriptions of actual physics at the Planck scale. The third context is directly connected to the use of AdS/CFT to describe real quark-gluon plasmas. In the latter context, we find that neither of the two duals are confirmed by the empirical data.

physics.hist-ph↗

arXiv2017

The Significance of Non-Empirical Confirmation in Fundamental Physics

In the absence of empirical confirmation, scientists may judge a theory's chances of being viable based on a wide range of arguments. The paper argues that such arguments can differ substantially with regard to their structural similarly to empirical confirmation. Arguments that resemble empirical confirmation in a number of crucial respects provide a better basis for reliable judgement and can, in a Bayesian sense, amount to significant \textit{non-empirical} confirmation. It is shown that three kinds of non-empirical confirmation that have been specified in earlier work do satisfy those conditions.

physics.hist-ph↗

arXiv1999

Holographic Cosmology and its Relevant Degrees of Freedom

We reconsider the options for cosmological holography. We suggest that a global and time--symmetric version of the Fischler-Susskind bound is the most natural generalization of the holographic bound encountered in AdS and De Sitter space. A consistent discussion of cosmological holography seems to imply an understanding of the notion of ``number of degrees of freedom'' that deviates from its simple definition as the entropy of the current state. The introduction of a more adequate notion of degree of freedom makes the suggested variation of the Fischler-Susskind bound look like a stringent and viable bound in all 4--dimensional cosmologies without a cosmological constant.

hep-th↗

arXiv1998

Higher Dimensional Operators in Top Condensation from a Renormalization Group Point of View

The predictive power of top-condensation models strongly depends on the behaviour of higher dimensional operators. These are analyzed in this paper by an extension of the standard renormalization group (RG) arguments which turns out to be a surprisingly powerful tool. Top-condensation models intermediated by underlying scalar exchange can be shown to be mere reparametrizations of the standard model. Further on, RG-arguments show that dynamical vector states cannot be lowered in top-condensation models. Finally we give a general argument concerning the size of higher dimensional operators of heavy vector exchange.

hep-ph↗

arXiv1997

SUSY violation in effective theories

We show that the effective theory of a supersymmetric model can violate SUSY at the level of dimension six operators and higher. This phenomenon occurs in gauge theories which involve heavy vector-superfields and different mass scales. It appears in SUSY GUT theories and is important in models of propagating Higgs boundstates.

hep-ph↗

arXiv1996

Propagating Higgs Boundstates in SUSY

The possibilities for an underlying theory behind an effective supersymmetric Nambu--Jona-Lasinio like model of electroweak symmetry breaking with propagating Higgs boundstates (e.g. supersymmetric topcondensation) are investigated. The concept of a renormalizable underlying theory turns out not to be appropriate. We argue that the new theory should come from the Planck scale and be connected to supergravity. Such a model can be constructed but necessarily implies a nonlinear definition of the full Lagrangian.

hep-ph↗

arXiv1995

Connections between Dynamical and Renormalization Group Techniques in Top Condensation Models

Predictions for the ratio $M_W/m_t$ arise in top condensation models from different methods. One type of prediction stems from Pagels--Stokar relations based on the use of Ward Identities in the calculation of the \GB decay constants and expresses $M_W$ in terms of integrals containing the dynamically generated mass function $Σ_t(p^2)$. Another type of prediction emerges from the renormalization group equations via infrared quasi--fixed--points of the running top quark Yukawa coupling. We demonstrate in this paper that in the limit of a high cutoff these two methods lead to the same predictions for $M_W/m_t$ and $M_W/M_H$ in lowest loop order.

hep-ph↗