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Profile: Amit Hagar (Indiana University, Bloomington)
  1. Amit Hagar, Chronicle of a Death Foretold.
    Scientific realism is dead, or so many philosophers believe. Its death was announced when philosophers became convinced that one can accept all scientific results without committing oneself to metaphysical existence claims about theoretical entities (Fine 1986, 112). In addition, the inability of self–proclaimed scientific realists, despite recurrent demands, to distinguish themselves from their rival anti–realists (Stein 1989) didn’t exactly help their cause. If realists cannot identify the key feature or features that set them apart from their opponents, then there is (...)
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  2. Amit Hagar, Review of M. Thalos' "Without Hierarchy" (OUP 2012).
  3. Amit Hagar, To Balance a Pencil on its Tip: On the Passive Approach to Quantum Error Correction.
    Quantum computers are hypothetical quantum information processing (QIP) devices that allow one to store, manipulate, and extract information while harnessing quantum physics to solve various computational problems and do so putatively more efficiently than any known classical counterpart. Despite many ‘proofs of concept’ (Aharonov and Ben–Or 1996; Knill and Laflamme 1996; Knill et al. 1996; Knill et al. 1998) the key obstacle in realizing these powerful machines remains their scalability and susceptibility to noise: almost three decades after their conceptions, experimentalists (...)
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  4. Amit Hagar, Thou Shalt Not Commute!
    For many among the scientifically informed public, and even among physicists, Heisenberg's uncertainty principle epitomizes quantum mechanics. Nevertheless, more than 86 years after its inception, there is no consensus over the interpretation, scope, and validity of this principle. The aim of this chapter is to offer one such interpretation, the traces of which may be found already in Heisenberg's letters to Pauli from 1926, and in Dirac's anticipation of Heisenberg's uncertainty relations from 1927, that stems form the hypothesis of finite (...)
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  5. Amit Hagar, Does Protective Measurement Tell Us Anything About Quantum Reality?
    An analysis of the two routes through which one may disentangle a quantum system from a measuring apparatus, hence protect the state vector of a single quantum system from being disturbed by the measurement, reveals several loopholes in the argument from protective measurement to the reality of the state vector of a single quantum system.
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  6. Amit Hagar & Giuseppe Sergioli (forthcoming). Counting Steps: A Finitist Interpretation of Objective Probability in Physics. Epistemologia.
    We propose a new interpretation of objective deterministic chances in statistical physics based on physical computational complexity. This notion applies to a single physical system (be it an experimental set--up in the lab, or a subsystem of the universe), and quantifies (1) the difficulty to realize a physical state given another, (2) the 'distance' (in terms of physical resources) from a physical state to another, and (3) the size of the set of time--complexity functions that are compatible with the physical (...)
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  7. Amit Hagar (2014). Demons in Physics. [REVIEW] Metascience 23 (2):1-10.
    In their book The Road to Maxwell's Demon Hemmo & Shenker re-describe the foundations of statistical mechanics from a purely empiricist perspective. The result is refreshing, as well as intriguing, and it goes against much of the literature on the demon. Their conclusion, however, that Maxwell's demon is consistent with statistical mechanics, still leaves open the question of why such a demon hasn't yet been observed on a macroscopic scale. This essay offers a sketch of what a possible answer could (...)
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  8. Amit Hagar (2014). Discrete or Continuous? The Quest for Fundamental Length in Modern Physics. Cambridge University Press.
    A book on the notion of fundamental length, covering issues in the philosophy of math, metaphysics, and the history and the philosophy of modern physics, from classical electrodynamics to current theories of quantum gravity. Published (2014) in Cambridge University Press.
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  9. Amit Hagar (2014). Squaring the Circle: Gleb Wataghin and the Prehistory of Quantum Gravity. Studies in the History and the Philosophy of Modern Physics 46:217-227.
    The early history of the attempts to unify quantum theory with the general theory of relativity is depicted through the work of the under--appreciated Italo-Brazilian physicist Gleb Wataghin, who is responsible for many of the ideas that the quantum gravity community is entertaining today.
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  10. Amit Hagar (2013). Review of Tim Maudlin's Philosophy of Physics: Space & Time. [REVIEW] Physics in Perspective (x).
  11. Meir Hemmo & Amit Hagar (2013). The Primacy of Geometry. Studies in the History and Philosophy of Modern Physics 44 (3):357-364.
    We argue that current constructive approaches to the special theory of relativity do not derive the geometrical Minkowski structure from the dynamics but rather assume it. We further argue that in current physics there can be no dynamical derivation of primitive geometrical notions such as length. By this we believe we continue an argument initiated by Einstein.
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  12. Amit Hagar (2012). Decoherence: The View From the History and the Philosophy of Science. Phil. Trans. Royal Soc. London A 375 (1975).
    We present a brief history of decoherence, from its roots in the foundations of classical statistical mechanics, to the current spin bath models in condensed matter physics. We analyze the philosophical import of the subject matter in three different foundational problems, and find that, contrary to the received view, decoherence is less instrumental to their solutions than it is commonly believed. What makes decoherence more philosophically interesting, we argue, are the methodological issues it draws attention to, and the question of (...)
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  13. Amit Hagar (2012). Veiled Realism? Review of B d'Espagnat's On Physics and Philosophy. [REVIEW] Physics in Perspective (x).
  14. Amit Hagar (2011). The Complexity of Noise: A Philosophical Outlook on Quantum Error Correction. Morgan & Claypool Publishers.
    In quantum computing, where algorithms exist that can solve computational problems more efficiently than any known classical algorithms, the elimination of errors that result from external disturbances or from imperfect gates has become the ...
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  15. Amit Hagar (2010). Review of Simon Saunders, Jonathan Barrett, Adrian Kent, David Wallace (Eds.), Many Worlds? Everett, Quantum Theory, and Reality. [REVIEW] Notre Dame Philosophical Reviews 2010 (10).
    Hugh Everett III died of a heart attack in July 1982 at the age of 51. Almost 26 years later, a New York Times obituary for his PhD advisor, John Wheeler, mentioned him and Richard Feynman as Wheeler’s most prominent students. Everett’s PhD thesis on the relative state formulation of quantum mechanics, later known as the “Many Worlds Interpretation”, was published (in its edited form) in 1957, and later (in its original, unedited form) in 1973, and since then has given (...)
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  16. Amit Hagar (2009). Active Fault‐Tolerant Quantum Error Correction: The Curse of the Open System. Philosophy of Science 76 (4):506-535.
    Relying on the universality of quantum mechanics and on recent results known as the “threshold theorems,” quantum information scientists deem the question of the feasibility of large‐scale, fault‐tolerant, and computationally superior quantum computers as purely technological. Reconstructing this question in statistical mechanical terms, this article suggests otherwise by questioning the physical significance of the threshold theorems. The skepticism it advances is neither too strong (hence is consistent with the universality of quantum mechanics) nor too weak (hence is independent of technological (...)
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  17. Amit Hagar (2009). Minimal Length in Quantum Gravity and the Fate of Lorentz Invariance. Studies in History and Philosophy of Science Part B 40 (3):259-267.
    Loop quantum gravity predicts that spatial geometry is fundamentally discrete. Whether this discreteness entails a departure from exact Lorentz symmetry is a matter of dispute that has generated an interesting methodological dilemma. On one hand one would like the theory to agree with current experiments, but, so far, tests in the highest energies we can manage show no such sign of departure. On the other hand one would like the theory to yield testable predictions, and deformations of exact Lorentz symmetry (...)
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  18. Amit Hagar (2008). Kant and Non-Euclidean Geometry. Kant-Studien 99 (1):80-98.
    It is occasionally claimed that the important work of philosophers, physicists, and mathematicians in the nineteenth and in the early twentieth centuries made Kant’s critical philosophy of geometry look somewhat unattractive. Indeed, from the wider perspective of the discovery of non-Euclidean geometries, the replacement of Newtonian physics with Einstein’s theories of relativity, and the rise of quantificational logic, Kant’s philosophy seems “quaint at best and silly at worst”.1 While there is no doubt that Kant’s transcendental project involves his own conceptions (...)
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  19. Amit Hagar (2008). Length Matters: The Einstein–Swann Correspondence and the Constructive Approach to the Special Theory of Relativity. Studies in History and Philosophy of Modern Physics 39 (3):532-556.
    I discuss a rarely mentioned correspondence between Einstein and Swann on the constructive approach to the special theory of relativity, in which Einstein points out that the attempts to construct a dynamical explanation of relativistic kinematical effects require postulating a fundamental length scale in the level of the dynamics. I use this correspondence to shed light on several issues under dispute in current philosophy of spacetime that were highlighted recently in Harvey Brown’s monograph Physical Relativity, namely, Einstein’s view on the (...)
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  20. Amit Hagar, Quantum Computing. Stanford Encyclopedia of Philosophy.
    Combining physics, mathematics and computer science, quantum computing has developed in the past two decades from a visionary idea to one of the most fascinating areas of quantum mechanics. The recent excitement in this lively and speculative domain of research was triggered by Peter Shor (1994) who showed how a quantum algorithm could exponentially "speed up" classical computation and factor large numbers into primes much more rapidly (at least in terms of the number of computational steps involved) than any known (...)
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  21. Amit Hagar (2007). Experimental Metaphysics2: The Double Standard in the Quantum-Information Approach to the Foundations of Quantum Theory. Studies in History and Philosophy of Modern Physics 38 (4):906-919.
    Among the alternatives of non-relativistic quantum mechanics (NRQM) there are those that give different predictions than quantum mechanics in yet-untested circumstances, while remaining compatible with current empirical findings. In order to test these predictions, one must isolate one’s system from environmental induced decoherence, which, on the standard view of NRQM, is the dynamical mechanism that is responsible for the ‘apparent’ collapse in open quantum systems. But while recent advances in condensed-matter physics may lead in the near future to experimental setups (...)
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  22. Amit Hagar (2007). Quantum Algorithms: Philosophical Lessons. [REVIEW] Minds and Machines 17 (2):233-247.
  23. Amit Hagar & Alex Korolev (2007). Quantum Hypercomputation—Hype or Computation? Philosophy of Science 74 (3):347-363.
    A recent attempt to compute a (recursion‐theoretic) noncomputable function using the quantum adiabatic algorithm is criticized and found wanting. Quantum algorithms may outperform classical algorithms in some cases, but so far they retain the classical (recursion‐theoretic) notion of computability. A speculation is then offered as to where the putative power of quantum computers may come from.
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  24. Amit Hagar & Meir Hemmo (2006). Explaining the Unobserved: Why Quantum Theory Ain't Only About Information. Foundations of Physics 36 (9):1295-1234.
    A remarkable theorem by Clifton, Bub and Halvorson (2003) (CBH) characterizes quantum theory in terms of information--theoretic principles. According to Bub (2004, 2005) the philosophical significance of the theorem is that quantum theory should be regarded as a ``principle'' theory about (quantum) information rather than a ``constructive'' theory about the dynamics of quantum systems. Here we criticize Bub's principle approach arguing that if the mathematical formalism of quantum mechanics remains intact then there is no escape route from solving the measurement (...)
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  25. Amit Hagar & Alexandre Korolev (2006). Quantum Hypercomputability? Minds and Machines 16 (1):87-93.
    A recent proposal to solve the halting problem with the quantum adiabatic algorithm is criticized and found wanting. Contrary to other physical hypercomputers, where one believes that a physical process “computes” a (recursive-theoretic) non-computable function simply because one believes the physical theory that presumably governs or describes such process, believing the theory (i.e., quantum mechanics) in the case of the quantum adiabatic “hypercomputer” is tantamount to acknowledging that the hypercomputer cannot perform its task.
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  26. Amit Hagar (2005). Discussion: The Foundations of Statistical Mechanics--Questions and Answers. Philosophy of Science 72 (3):468-478.
    Huw Price (1996, 2002, 2003) argues that causal-dynamical theories that aim to explain thermodynamic asymmetry in time are misguided. He points out that in seeking a dynamical factor responsible for the general tendency of entropy to increase, these approaches fail to appreciate the true nature of the problem in the foundations of statistical mechanics (SM). I argue that it is Price who is guilty of misapprehension of the issue at stake. When properly understood, causal-dynamical approaches in the foundations of SM (...)
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  27. Amit Hagar (2005). Quantum Information - What Price Realism? Intl. J. Of Quantum Information 3 (1):165-170.
    Recent suggestions to supply quantum mechanics (QM) with realistic foundations by reformulating it in light of quantum information theory (QIT) are examined and are found wanting by pointing to a basic conceptual problem that QIT itself ignores, namely, the measurement problem. Since one cannot ignore the measurement problem and at the same time pretend to be a realist, as they stand, the suggestions to reformulate QM in light of QIT are nothing but instrumentalism in disguise.
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  28. Amit Hagar (2004). Chance and Time. Dissertation, UBC
    One of the recurrent problems in the foundations of physics is to explain why we rarely observe certain phenomena that are allowed by our theories and laws. In thermodynamics, for example, the spontaneous approach towards equilibrium is ubiquitous yet the time-reversal-invariant laws that presumably govern thermal behaviour in the microscopic level equally allow spontaneous departure from equilibrium to occur. Why are the former processes frequently observed while the latter are almost never reported? Another example comes from quantum mechanics where the (...)
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  29. Amit Hagar (2003). A Philosopher Looks at Quantum Information Theory. Philosophy of Science 70 (4):752-775.
    Recent suggestions to supply quantum mechanics (QM) with realistic foundations by reformulating it in light of quantum information theory (QIT) are examined and are found wanting by pointing to a basic conceptual problem that QIT itself ignores, namely, the measurement problem. Since one cannot ignore the measurement problem and at the same time pretend to be a realist, as they stand, the suggestions to reformulate QM in light of QIT are nothing but instrumentalism in disguise.
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  30. Amit Hagar (2002). Thomas Reid and Non-Euclidean Geometry. Reid Studies 5 (2):54-64.
    In the chapter “The Geometry of Visibles” in his ‘Inquiry into the Human Mind’, Thomas Reid constructs a special space, develops a special geometry for that space, and offers a natural model for this geometry. In doing so, Reid “discovers” non-Euclidean Geometry sixty years before the mathematicians. This paper examines this “discovery” and the philosophical motivations underlying it. By reviewing Reid’s ideas on visible space and confronting him with Kant and Berkeley, I hope, moreover, to resolve an alleged impasse in (...)
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