Christopher T. Hill

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Christopher T. Hill
ChristopherTHillphysics.jpg
Born (1951-06-19) June 19, 1951 (age 72)
Nationality American
Alma mater Massachusetts Institute of Technology (BS, MS)
California Institute of Technology (PhD)
Known for Infrared fixed point of the top quark; Topcolor; Top quark condensate; Dimensional deconstruction; Chiral symmetry breaking in Heavy-Light Mesons; Theory of UHE Cosmic Rays; Soft Nambu-Goldstone Boson model of Dark Matter.
Scientific career
Institutions Fermilab
Thesis Higgs scalars and the nonleptonic weak interactions  (1977)
Doctoral advisor Murray Gell-Mann

Christopher T. Hill (born June 19, 1951) is an American theoretical physicist at the Fermi National Accelerator Laboratory who did undergraduate work in physics at M.I.T. (B.S., M.S., 1972), and graduate work at Caltech (Ph.D., 1977, Murray Gell-Mann [1] ). Hill's Ph.D. thesis, "Higgs Scalars and the Nonleptonic Weak Interactions" (1977) contains one of the first detailed discussions of the two-Higgs-doublet model and its impact upon weak interactions. [2] His work mainly focuses on new physics that can be probed in laboratory experiments or cosmology.

Contents

Hill is an originator, with William A. Bardeen and Manfred Lindner, of the idea that the Higgs boson is composed of top and anti-top quarks. This emerges from the concept of the top quark infrared fixed point, [3] which predicted (1981) that the top quark would be very heavy, contrary to most popular ideas at the time. The fixed point prediction lies within 20% of the observed top quark mass (1995). This implies that the top quarks may be strongly coupled at very short distances and could form a composite Higgs boson, which led to top quark condensates, [4] topcolor, [5] [6] and dimensional deconstruction, a renormalizable lattice description of extra dimensions of space. [7] The original minimal top condensation model predicted the Higgs boson mass to be about twice the observed value of 125 GeV, but extensions of the theory achieve concordance with both the Higgs boson and top quark masses. Several new heavy Higgs bosons, such as a b-quark scalar bound state, may be accessible to the LHC. [8] [9] [10]

Hill coauthored (with Elizabeth H. Simmons) a comprehensive review of strong dynamical theories and electroweak symmetry breaking that has shaped many of the experimental searches for new physics at the Tevatron and LHC. [11]

Heavy-light mesons contain a heavy quark and a light anti-quark, and provide a window on the chiral symmetry dynamics of a single light quark. Hill and Bardeen showed that the (spin)parity ground states are split from the parity partners by a universal mass gap of about due to the light quark chiral symmetry breaking. [12] This correctly predicted an abnormally long-lived resonance, the (and the now confirmed ), ten years before its discovery, and numerous decay modes which have been confirmed by experiment. [13] Similar phenomena should be seen in the mesons and (heavy-heavy-strange baryons).

Hill has worked on topological interactions and, with collaborators, was first to obtain the full Wess-Zumino-Witten term for the standard model which describes the physics of the chiral anomaly in Lagrangians, including pseudoscalars, spin-1 vector mesons, and the and . The WZW term requires a non-trivial counter-term to map the "consistent" anomaly into the "covariant" anomaly, as dictated by the conserved currents of the standard model. With the full WZW-term, new anomalous interactions were revealed such as the vertex. This leads to where is a heavy nucleus, and may contribute to excess photons seen in low energy neutrino experiments. [14] The result reproduces B+L violation by the anomaly in the standard model, and predicts numerous other anomalous processes. Hill has given a derivation of the coefficients of consistent and covariant chiral anomalies (even D), and Chern-Simons terms (odd D), without resorting to fermion loops, from the Dirac monopole construction and its generalization ("Dirac Branes") to higher dimensions. [15]

Hill is an originator of cosmological models of dark energy and dark matter based upon ultra-low mass pseudo-Nambu-Goldstone bosons associated with symmetries of neutrino masses. He proposed that the cosmological constant is connected to the neutrino mass, as [16] [17] and developed modern theories of the origin of ultra-high-energy nucleons and neutrinos from grand unification relics. [18] [19] [20] [21] He has shown that a cosmic axion field will induce an effective oscillating electric dipole moment for any magnet. [22] [23]

With Graham Ross he focused on spontaneously broken scale symmetry (or Weyl symmetry), where the scale of gravity (Planck mass) and the inflationary phase of the ultra-early universe are generated together as part of a unified phenomenon dubbed "inertial symmetry breaking." [24] [25] [26] Here the Weyl symmetry breaking occurs because the Noether current is the derivative of a scalar operator, called the "kernal." During a period of pre-Planckian expansion the current must red-shift to zero, hence the kernal red-shifts to a constant value which determines the Planck mass and the Einstein Hilbert action then emerges.

Hill has returned to the issue of composite scalars in relativistic field theory, such as the Higgs boson, and the role of the internal structure of the bound state.

Academic Positions and Honors

Books and Articles

Hill has authored three popular books with Nobel laureate Leon Lederman about physics and cosmology, and the commissioning of the Large Hadron Collider.

Related Research Articles

References

  1. "Murray Gell-Mann," Physics Today, (2020); https://physicstoday.scitation.org/doi/10.1063/PT.3.4480 (2020)
  2. "Higgs Scalars and the Nonleptonic Weak Interactions" (1977)
  3. Hill, Christopher T. (1 August 1981). "Quark and lepton masses from renormalization-group fixed points". Physical Review D. 24 (3): 691–703. Bibcode:1981PhRvD..24..691H. doi:10.1103/PhysRevD.24.691.
  4. Bardeen, William A.; Hill, Christopher T.; Lindner, Manfred (1990). "Minimal dynamical symmetry breaking of the standard model". Phys. Rev. D. 41 (5): 1647–1660. Bibcode:1990PhRvD..41.1647B. doi:10.1103/PhysRevD.41.1647. PMID   10012522.
  5. Hill, Christopher T. (1995). "Topcolor Assisted Technicolor". Phys. Lett. B. 345 (4): 483–489. arXiv: hep-ph/9411426 . Bibcode:1995PhLB..345..483H. doi:10.1016/0370-2693(94)01660-5. S2CID   15093335.
  6. Hill, Christopher T. (1991). "Topcolor: top quark condensation in a gauge extension of the standard model". Physics Letters B. 266 (3–4): 419–424. Bibcode:1991PhLB..266..419H. doi:10.1016/0370-2693(91)91061-Y. S2CID   121635635.
  7. Hill, Christopher T.; Pokorski, Stefan; Wang, Jing (2001). "Gauge invariant effective Lagrangian for Kaluza-Klein modes". Phys. Rev. D. 64 (10): 105005. arXiv: hep-th/0104035 . Bibcode:2001PhRvD..64j5005H. doi:10.1103/physrevd.64.105005. S2CID   7377062.
  8. Hill, Christopher T. (4 April 2014). "Is the Higgs boson associated with Coleman-Weinberg dynamical symmetry breaking?". Physical Review D. 89 (7): 073003. arXiv: 1401.4185 . Bibcode:2014PhRvD..89g3003H. doi:10.1103/PhysRevD.89.073003. S2CID   119192830.
  9. Hill, Christopher T.; Machado, Pedro; Thomsen, Anders; Turner, Jessica (2019). "Where are the Next Higgs Bosons?". Physical Review. D100 (1): 015051. arXiv: 1904.04257 . Bibcode:2019PhRvD.100a5051H. doi:10.1103/PhysRevD.100.015051. S2CID   104291827.
  10. Hill, Christopher T.; Machado, Pedro; Thomsen, Anders; Turner, Jessica (2019). "Scalar Democracy". Physical Review. D100 (1): 015015. arXiv: 1902.07214 . Bibcode:2019PhRvD.100a5015H. doi:10.1103/PhysRevD.100.015015. S2CID   119193325.
  11. Hill, Christopher T.; Simmons, Elizabeth H. (2003). "Strong dynamics and electroweak symmetry breaking". Phys. Rep. 381 (4–6): 235. arXiv: hep-ph/0203079 . Bibcode:2003PhR...381..235H. doi:10.1016/S0370-1573(03)00140-6. S2CID   118933166.
  12. Bardeen, William A.; Hill, Christopher T. (1994). "Chiral dynamics and heavy quark symmetry in a solvable toy field theoretic model". Physical Review D. 49 (1): 409–425. arXiv: hep-ph/9304265 . Bibcode:1994PhRvD..49..409B. doi:10.1103/PhysRevD.49.409. PMID   10016779. S2CID   1763576.
  13. Bardeen, William A.; Eichten, Estia; Hill, Christopher T. (2003). "Chiral multiplets of heavy-light mesons". Physical Review D. 68 (5): 054024. arXiv: hep-ph/0305049 . Bibcode:2003PhRvD..68e4024B. doi:10.1103/PhysRevD.68.054024. S2CID   10472717.
  14. Harvey, Jeffrey A.; Hill, Christopher T.; Hill, Richard (2007). "Standard Model Gauging of the Wess-Zumino-Witten Term: Anomalies, Global Currents and pseudo-Chern-Simons Interactions". Phys. Rev. D. 30 (8): 085017. arXiv: 0712.1230 . doi:10.1103/PhysRevD.77.085017.
  15. C. T. Hill, "Dirac Branes and Anomalies/Chern-Simons terms in any D," arXiv:0907.1101 [hep-th]. For fermion loops see: "Lecture notes for massless spinor and massive spinor triangle diagrams," arXiv:hep-th/0601155 [hep-th].
  16. Frieman, Joshua A.; Hill, Christopher T.; Stebbins, Albert; Waga, Ioav (1995). "Cosmology with ultralight pseudo Nambu-Goldstone bosons". Phys. Rev. Lett. 75 (11): 2077–2080. arXiv: astro-ph/9505060 . Bibcode:1995PhRvL..75.2077F. doi:10.1103/PhysRevLett.75.2077. PMID   10059208. S2CID   11755173.
  17. Hill, Christopher T.; Schramm, David N.; Fry, James N. (1989). "Cosmological Structure Formation from Soft Topological Defects" (PDF). Comments on Nucl. Part. Phys. Vol. 19. pp. 25–39.
  18. Hill, Christopher T.; Schramm, David N. (1 February 1985). "Ultrahigh-energy cosmic-ray spectrum". Physical Review D. 31 (3): 564–580. Bibcode:1985PhRvD..31..564H. doi:10.1103/PhysRevD.31.564. PMID   9955721.
  19. Hill, Christopher T.; Schramm, David N.; Walker, Terry P. (1987). "Ultrahigh-Energy Cosmic Rays from Superconducting Cosmic Strings". Phys. Rev. D. 36 (4): 1007–1016. Bibcode:1987PhRvD..36.1007H. doi:10.1103/physrevd.36.1007. PMID   9958264.
  20. Bhattacharjee, Pijushpani; Hill, Christopher T.; Schramm, David N. (1992). ""Grand unified theories," topological defects and ultrahigh-energy cosmic rays". Phys. Rev. Lett. 69 (4): 567–570. Bibcode:1992PhRvL..69..567B. doi:10.1103/PhysRevLett.69.567. hdl: 2060/19920009031 . PMID   10046974. S2CID   20633612.
  21. Hill, Christopher T. (1983). "Monopolonium". Nuclear Physics B. 224 (3): 469–490. Bibcode:1983NuPhB.224..469H. doi:10.1016/0550-3213(83)90386-3. OSTI   1155484.
  22. Hill, Christopher T. (2015). "Axion Induced Oscillating Electric Dipole Moments". Physical Review D. 224 (3): 111702. arXiv: 1504.01295 . Bibcode:2015PhRvD..91k1702H. doi:10.1103/PhysRevD.91.111702. OSTI   1212736. S2CID   96444192.
  23. Hill, Christopher T. (2016). "Axion Induced Oscillating Electric Dipole Moment of the Electron". Physical Review D. 224 (3): 025007. arXiv: 1508.04083 . Bibcode:2016PhRvD..93b5007H. doi:10.1103/PhysRevD.93.025007. OSTI   1223242. S2CID   119221466.
  24. Ferreira, Pedro G.; Hill, Christopher T.; Ross, Graham G. (8 February 2017). "Weyl current, scale-invariant inflation, and Planck scale generation". Physical Review D. 95 (4): 043507. arXiv: 1610.09243 . Bibcode:2017PhRvD..95d3507F. doi:10.1103/PhysRevD.95.043507. S2CID   119269154.
  25. Ferreira, Pedro G.; Hill, Christopher T.; Ross, Graham G. (2018). "Inertial Spontaneous Symmetry Breaking and Quantum Scale Invariance". Physical Review D. 98 (11): 116012. arXiv: 1801.07676 . Bibcode:2018PhRvD..98k6012F. doi:10.1103/PhysRevD.98.116012. S2CID   119267087.
  26. Hill, Christopher T.; Ross, Graham G. (2020). "Gravitational Contact Terms and the Physical Equivalence of Weyl Transformations in Effective Field Theory". Physical Review D. 102: 125014. arXiv: 2009.14782 . doi:10.1103/PhysRevD.102.125014. S2CID   222067042.
  27. "APS Fellow Archive". American Physical Society. (search on year=1989 and institution=Fermi National Accelerator Laboratory)