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Roman Jackiw
Roman Jackiw
Roman Jackiw
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Roman Wladimir Jackiw[a] (/ˈroʊmɑːn ˈdʒɑːkiːv/; Polish: [ˈrɔman ˈjakʲiv]; November 8, 1939 – June 14, 2023) was a Polish-born American theoretical physicist and Dirac Medallist.

Key Information

Biography

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Born in Lubliniec, Poland in 1939[1] to a Ukrainian family, the family later moved to Austria and Germany before settling in New York City when Jackiw was about 10.[2]

Jackiw earned his undergraduate degree from Swarthmore College and his PhD from Cornell University in 1966 under Hans Bethe and Kenneth Wilson. He was a professor at the Massachusetts Institute of Technology Center for Theoretical Physics from 1969 until his retirement. He retained his affiliation in emeritus status in 2019.[3]

Jackiw co-discovered the chiral anomaly, which is also known as the Adler–Bell–Jackiw anomaly. In 1969, he and John Stewart Bell published their explanation, which was later expanded and clarified by Stephen L. Adler, of the observed decay of a neutral pion into two photons. This decay is forbidden by a symmetry of classical electrodynamics, but Bell and Jackiw showed that this symmetry cannot be preserved at the quantum level. Their introduction of an "anomalous" term from quantum field theory required that the sum of the charges of the elementary fermions had to be zero. This work also gave important support to the colour theory of quarks.

Jackiw is also known for Jackiw–Teitelboim gravity, often abbreviated as JT Gravity, a theory of gravity with one dimension each of space and time that includes a dilaton field. Sometimes known as the R = T model, it is used to model some aspects of near-extremal black holes.[4]

Jackiw married fellow physicist So-Young Pi, daughter of Korean writer Pi Chun-deuk. One of Jackiw's sons is Stefan Jackiw, an American violinist. The other is Nicholas Jackiw, a software designer known for inventing The Geometer's Sketchpad. His daughter, Simone Ahlborn, is an educator at Moses Brown School in Providence, Rhode Island.

Jackiw died 14 June 2023, at the age of 83.[5]

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References

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Roman Jackiw

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Roman Jackiw (November 8, 1939 – June 14, 2023) was a Polish-born American theoretical physicist whose pioneering work in profoundly influenced , , and gravitational physics over more than five decades. Born in Lubliniec, , to Ukrainian heritage parents, he emigrated to the as a child and earned a in physics from in 1961, followed by a PhD from in 1966 under . After serving as a junior fellow at from 1966 to 1969, Jackiw joined the (MIT) in 1969, where he held the Jerrold R. Zacharias Chair of Physics until becoming professor emeritus in 2014, spending a total of 54 years at the institution. Jackiw's most celebrated contribution came early in his career with the discovery of the Adler–Bell–Jackiw (ABJ) anomaly in 1969 with John Bell (independently predicted by Stephen Adler), which resolved key puzzles in , such as the decay of the neutral pion into two photons and the U(1) problem in by explaining the η′ meson's mass. This "anomalous" term in field theory provided crucial support for the quark color model and highlighted quantum effects breaking classical symmetries. Building on this, Jackiw, collaborating with Rebbi, introduced the concept of theta-vacua in in the 1970s, linking non-perturbative effects to the neutron's and inspiring the as a candidate, though it remains a point of tension in the . He also pioneered the discovery of fractional fermion number and spin in models with Rebbi in 1976, demonstrating how topological structures in field theories could produce fractional charges observable in condensed matter quasiparticles. Throughout his career, Jackiw applied innovatively across disciplines, including the development of the Jackiw–Teitelboim model of two-dimensional gravity with Claudio Teitelboim in 1985, which serves as a simplified framework for studying entropy and effects. His research extended to topological mass terms, current algebra, and the integration of field theory with gravitational phenomena, resulting in over 200 publications and several influential textbooks, such as Intermediate Quantum Mechanics (multiple editions) and Diverse Topics in Theoretical and (1995). Jackiw's work earned him prestigious honors, including the Dannie Heineman Prize for in 1995 from the , the Dirac Medal in 1998 from the , and election to the in 1998. He was also a foreign member of the Ukrainian National Academy of Sciences and received honorary doctorates from universities including , , , and Montréal. In addition to his scholarly impact, Jackiw mentored generations of physicists at MIT's Center for and maintained strong international ties, including visiting positions at institutions like and UCLA. He was married to So-Young Pi, with whom he collaborated, and was survived by three children. Jackiw's legacy endures through his elucidation of quantum anomalies, topological phenomena, and the unexpected efficacy of field theory in unifying disparate areas of physics.

Early life and education

Family background and early years

Roman Jackiw was born Roman Volodymyr Yatskiv on November 8, 1939, in Lubliniec, , to parents of Ukrainian heritage, displaced by . In 1942, amid the escalating dangers of and Nazi occupation, his father relocated the family from to and then to to evade the conflict; they remained displaced until immigrating to the as refugees in 1949, when Jackiw was about 10 years old. The family settled in , where Jackiw's father anglicized their surname from Yatskiv to Jackiw upon arrival. Jackiw spent his childhood in New York, attending junior high school under the Xaverian monks and high school with the Christian Brothers, which provided a structured environment amid his family's adjustment to life in America. His initial fascination with physics emerged during these years through self-directed reading, particularly after encountering George Gamow's book , which ignited his passion for the subject. This early curiosity paved the way for his transition to undergraduate studies at .

Academic training

Roman Jackiw earned his degree in physics from in 1961, complemented by minors in the and . He pursued graduate studies at , where he completed his PhD in physics in 1966 under the joint supervision of and Kenneth G. Wilson. Jackiw's doctoral thesis, titled "Nonperturbative Solutions of the Bethe-Salpeter Equation for the Vertex Function," addressed key aspects of , focusing on the high-energy behavior of form factors in through nonperturbative methods. Following his doctorate, Jackiw held a junior fellowship in Harvard University's Society of Fellows from 1966 to 1969, during which he collaborated with and others on developments in effective field theories within .

Academic career

Positions and appointments

Following his PhD from in 1966, Jackiw held a junior fellowship at from 1966 to 1969. In 1969, he joined the Massachusetts Institute of Technology (MIT) as an in the Department of Physics, advancing to and full professor. He was appointed the Jerrold R. Zacharias Professor of Physics, a position he held until his retirement. Jackiw became professor emeritus in 2013 and remained active in research at MIT until his death on June 14, 2023. Throughout his tenure, he took on visiting appointments, including a and visiting professorship at from 1977 to 1978.

Mentorship and collaborations

Jackiw supervised over 30 PhD students at MIT over the course of his long-term faculty position there, fostering a distinctive school of that integrated advanced mathematical tools with . Among his notable doctoral advisees were Estia Eichten, now a at ; Joseph Lykken, a researcher at ; and Andrew , a professor at . His mentorship style combined rigorous intellectual scrutiny with personal encouragement, leaving a lasting impact on students who went on to prominent careers in academia and research institutions. A key aspect of Jackiw's collaborative work was his extensive partnership with So-Young Pi, his wife and fellow at , resulting in 46 joint publications spanning topics in such as conformal symmetries, solitons, and Chern-Simons gauge theories. Their co-authorships often explored supersymmetric extensions and dynamical aspects of field theories, reflecting a productive academic and personal alliance that influenced developments in these areas. Jackiw played a significant role in organizing workshops and seminars on at MIT during the 1970s and 1980s, including co-founding the joint Harvard-MIT seminar series, which became a vital forum for exchanging ideas among leading physicists. He also co-edited proceedings for landmark events like the 1983 Shelter Island Conference on and the Fundamental Problems of Physics, which brought together experts to discuss foundational challenges in the field. These initiatives helped cultivate a vibrant intellectual environment at MIT and beyond. Following his death in 2023, tributes from the community underscored Jackiw's profound influence through informal , with former students and colleagues recalling his generous guidance, candid feedback, and role in nurturing talent across generations. Figures like Strominger highlighted how Jackiw's support extended beyond formal advising, shaping careers and fostering collaborative networks in and related disciplines.

Research contributions

Quantum anomalies and field theory

Roman Jackiw made foundational contributions to , particularly through his work on anomalies that reveal inconsistencies between classical symmetries and their quantum realizations. In , Jackiw collaborated with John S. Bell to discover the , also known as the Adler–Bell–Jackiw anomaly (independent of Stephen Adler's contemporaneous work), which demonstrates the breakdown of in (QED). This anomaly arises in the perturbative calculation of the triangle diagram involving two electromagnetic currents and one axial current, resolving apparent infinities and non-renormalizability issues that had puzzled earlier formulations of QED. The discovery provided a quantum mechanical explanation for the observed non-conservation of the axial current, such as in weak interactions where appears violated. The anomaly manifests in the of the axial current, given by the ∂μJ5μ=e216π2ϵμνρσFμνFρσ,\partial_\mu J^\mu_5 = \frac{e^2}{16\pi^2} \epsilon^{\mu\nu\rho\sigma} F_{\mu\nu} F_{\rho\sigma}, where J5μJ^\mu_5 is the axial vector current, ee is the electron charge, ϵμνρσ\epsilon^{\mu\nu\rho\sigma} is the Levi-Civita tensor, and FμνF_{\mu\nu} is the strength tensor. This expression, derived through point-splitting regularization to handle ultraviolet divergences, quantifies the anomalous violation proportional to the topological density of the gauge field. Historically, the calculation addressed ambiguities in renormalizing the pseudoscalar density operator in QED, showing that the anomaly is finite and unambiguous after proper regularization, thus restoring consistency to the . Jackiw and Bell's work complemented Adler's contemporaneous derivation, establishing the anomaly as a universal feature of gauge theories with chiral fermions. One key application of the anomaly is to the decay of the neutral pion (π0→γγ\pi^0 \to \gamma\gamma), which classical would forbid but is observed experimentally with a lifetime of approximately 8.5×10−178.5 \times 10^{-17} seconds. The anomaly provides the leading-order amplitude for this process via the triangle diagram, matching the measured decay rate and confirming the model's prediction of three colors when including effects. In weak interactions, the anomaly similarly explains the non-conservation of helicity, linking microscopic quantum effects to macroscopic phenomena like parity violation. In the and , Jackiw's early research laid groundwork for anomaly studies through investigations into procedures and effective Lagrangians. His PhD thesis explored nonperturbative solutions to the Bethe-Salpeter for the vertex function in spinor electrodynamics, addressing high-momentum dynamics and in QED. Building on this, Jackiw contributed to current algebra frameworks, developing effective Lagrangians that incorporate partially conserved axial currents (PCAC) and chiral symmetries for low-energy physics. These efforts, including field-theoretic analyses of sum rules and Ward identities, facilitated the integration of ideas into effective theories, influencing later anomaly derivations.

Topological and geometric phenomena

In collaboration with Claudio Rebbi, Roman Jackiw introduced the concept of theta-vacua in Yang-Mills quantum theory in 1976, proposing a structure where the vacuum is a superposition of states labeled by a continuous parameter θ, arising from the periodic nature of gauge transformations and the role of pseudoparticle solutions like instantons. This framework was pivotal for quantum chromodynamics (QCD), as it provided the basis for understanding non-perturbative vacuum effects that resolve the U(1) axial anomaly problem through instanton-induced symmetry breaking, explaining the absence of a light η' meson. Building on his foundational work in quantum anomalies, Jackiw's theta-vacuum insights highlighted how topological configurations underpin chiral symmetry violation in QCD. In the same year, Jackiw and Rebbi developed the Jackiw-Rebbi model, a one-dimensional system coupling Dirac fermions to a kink, which demonstrates the emergence of zero-energy bound states and fractional fermion number 1/2 due to the topological nature of the background. This model illustrates how index theorems in bind to topological defects, leading to protected zero modes that carry fractional charges and have implications for understanding in lower-dimensional systems. The work established a paradigm for fermion-soliton interactions, influencing studies of topological insulators and domain walls in . During the 1980s, Jackiw extended his investigations into topological solitons, including magnetic monopoles, where he uncovered hidden dynamical symmetries such as O(3) × O(2,1) in the charged particle-monopole system, revealing scale-invariant classical trajectories and quantum spectra analogous to hydrogenic atoms. His analysis of monopoles emphasized geometric and topological invariants that govern and bound states, connecting to broader structures. Complementing this, Jackiw explored skyrmions as stable topological configurations in nonlinear sigma models, contributing to interpretations of baryons as solitons with quantized winding numbers that preserve topological charge under deformations. In parallel, he examined geometric phases in , particularly in systems with conical singularities or spinning geometries, where adiabatic transport around defects induces Berry-like phases dependent on solid angles and spin, unifying Aharonov-Bohm effects with monopole geometries. Jackiw's pioneering work on the Chern-Simons term in the 1980s provided a gauge-invariant formulation of topologically massive electrodynamics in three dimensions, where the term generates parity-odd interactions and massive gauge bosons without Higgs mechanisms. This construction proved essential for describing anyons—particles with fractional statistics intermediate between bosons and fermions—in two-dimensional systems, as the Chern-Simons flux attachment transmutes via topological linking. In the 1990s, these ideas were applied to the , where Jackiw's framework supported models by attaching flux quanta to electrons, explaining quantized Hall conductances and the hierarchy of filling fractions through effective Chern-Simons gauge fields. His contributions underscored the role of topological terms in realizing exotic quasiparticles and edge states in strongly correlated systems.

Gravity models and black holes

Roman Jackiw made significant contributions to gravitational theories in lower dimensions, particularly through his development of models that serve as tractable frameworks for studying quantum aspects of . In collaboration with Teitelboim, Jackiw helped formulate what is known as Jackiw–Teitelboim (JT) , a simplified model of in two dimensions (1+1D) introduced in 1985. This model incorporates a field Φ coupled to the Ricci scalar, providing an exactly solvable theory that captures essential features of higher-dimensional , such as horizons and , while avoiding many complexities of full . The JT action is given by S=116πG∫d2x−g Φ(R+2Λ)+boundary terms,S = \frac{1}{16\pi G} \int d^2 x \sqrt{-g} \, \Phi (R + 2\Lambda) + \text{boundary terms},
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