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Electroweak Symmetry Breaking (Historical Perspective) Electroweak Symmetry Breaking (Historical Perspective) 40th SLAC Summer Institute · 2012 History is not just a thing of the past! 2 Symmetry Indistinguishable before and after a transformation Unobservable quantity would vanish if symmetry held Disorder order = reduced symmetry 3 Symmetry Bilateral Translational, rotational, … Ornamental Crystals 4 Symmetry CsI Fullerene C60 ball and stick created from a PDB using Piotr Rotkiewicz's [http://www.pirx.com/iMol/ iMol]. {{gfdl}} Source: English Wikipedia, 5 Symmetry (continuous) 6 Symmetry matters. 7 8 Symmetries & conservation laws Spatial translation Momentum Time translation Energy Rotational invariance Angular momentum QM phase Charge 9 Symmetric laws need not imply symmetric outcomes. 10 symmetries of laws ⇏ symmetries of outcomes by Wilson Bentley, via NOAA Photo Library Photo via NOAA Wilson Bentley, by Studies among the Snow Crystals ... CrystalsStudies amongSnow the ... 11 Broken symmetry is interesting. 12 Two-dimensional Ising model of ferromagnet http://boudin.fnal.gov/applet/IsingPage.html 13 Continuum of degenerate vacua 14 Nambu–Goldstone bosons V Betsy Devine Yoichiro Nambu �� 2 Massless NG boson 1 Massive scalar boson NGBs as spin waves, phonons, pions, … Jeffrey Goldstone 15 Symmetries imply forces. I: scale symmetry to unify EM, gravity Hermann Weyl (1918, 1929) 16 NEW Complex phase in QM ORIGINAL Global: free particle Local: interactions 17 Maxwell’s equations; QED massless spin-1 photon coupled to conserved charge no impediment to electron mass (eL & eR have same charge) James Clerk Maxwell (1861/2) 18 19 QED Fermion masses allowed Gauge-boson masses forbidden Photon mass term 1 2 µ 2 mγ A Aµ violates gauge invariance: AµA (Aµ ∂µΛ) (A ∂ Λ) = AµA µ ⇥ − µ − µ ⇤ µ Massless photon predicted 22 observed: mγ 10− me 20 Symmetries imply forces. II: non-Abelian gauge symmetry Robert Mills C. N. Yang Ron Shaw (1954) 21 Can one choose independently at each point in spacetime the convention to name proton and neutron? Local isospin symmetry implies 3 massless gauge bosons ☹ coupled to isospin no impediment to nucleon mass (NL & NR have same isospin) 22 Might hiding the symmetry help? Seems to add massless NGBs ☹ to massless gauge bosons ☹ Goldstone theorem proved with ever-increasing rigor 23 Gerrit-Jan Flim (left) and Heike Kamerlingh Onnes at the helium liquefactor, ca. 1920 (Leiden Institute of Physics). Dirk van Delft | MUSEUM BOERHAAVE, LEIDEN UNIVERSITY HEIKE KAMERLINGH ONNES AND THE ROAD TO LIQUID HELIUM Superconductivity (1911) In 1908, Heike Kamerlingh Ontricnes effectfirst liquefied in the helium voltage in a cryogenic leads by making more with broken mercury threads! Fig.7 Original drawing by Gerrit Jan Flim showing the setup for the persistent-current experiments lead immersed in liquid helium and laboratory whose excellence and scale were unparalleled. Creating, staffing of May 1914. Left: front view showing the lead coil in the helium cryostat and the copper and running the Leiden laboaratory required more than just scientific skill. everything of the same metal. It didn’t The generation of strong magnetic fields compensation coil in the liquid air Dewar (actually, during the experiment, both coils were on carrying a persistent current of 200 A. work, because the transition from solid now became within reach. But the ex- the same height as the compass needle). Right: top view showing also the compass needle in Today, the most compelling demon- On 10 July 1908, Heike Kamerlingh Onnes Heike Kamerlingh Onnes was born in fruitful exchange between theory and the middle pointing north demonstrating good compensation of the fields from the Pb and the (1853-1926) liquified helium for the the cityto of Groningenliquid in 1853mercury [1]. His experiment. turned out to be the periment, even announced in Kamer- stration of persistent currents is the first time, briefly rendering his Dutch father owned a tile factory in a small copper coils (Archive of the Museum Boerhaave, Leiden). laboratory ‘the coldest spot on earth’. village,source a two hour drive of on a horseback. considerable MISSION thermoelectric lingh Onnes’s Nobel lecture and carried levitation of a permanent magnet by a This paper tells the story of Leiden Uni- Heike studied at the University of Gro- When Kamerlingh Onnes started as versity’s famed cryogenics laboratory ningen.voltage At the age of 17 ofhe started 0.5 stud- mV.a professor Still, in theexperimental October physics ex- out on 17 January 1914, brought a great superconductor. and the man behind it, whose scientific ying chemistry, his favourite topic at in Leiden in 1882, he immediately de- accomplishments earned him the No- high school.periment After passing hisproduced propae- cided to transformthe thehistoric building into a plot, deception. The magnetic field generated The excitement about persistent cur- bel Prize in Physics in 1913. The central deutic exam he moved to Heidelberg, research laboratory. Why this consid- question is how Kamerlingh Onnes then famous for its international aca- erable effort? Because of his scientific was able to succeed so brilliantly in demicshown environment, forin a Wanderjahr Fig.6 mission:, of tothe test the abruptmolecular laws ofreap- with a lead coil turned out to destroy rents on a macro scale spread quickly. developing his cryogenics laboratory (year of travel). Why Heidelberg? Be- Johannes Diderik van der Waals and in – undoubtedly an exceptional feat in cause pearanceof Robert Bunsen, in of those thedays doingmercury so to give international resistance prestige at the superconductivity at 4.2 K already Paul Ehrenfest, who witnessed the terms of its scale and its almost in- the most famous chemist in Europe. to Dutch physics. Van der Waals had dustrial approach at the turn of the In his4.20 first semester, K. HeikeThe enjoyed part the publishedof the his thesis plot on the abovecontinuity the at 600 Gauss (60 mT). Gone were the experiment, wrote in a letter to H.A. century. Key factors in his success were chemistry lab very much. But when the of the liquid and gas phase in 1873, a Kamerlingh Onnes’s organisational time cametransition to start some own research,temperature milestone in molecular (TC physics) is – noticeof par- dreams of producing magnetic fields as Lorentz: “Unsettling, to see the ring talent, his personality and his inter- Bunsen’s conservatism and aversion that molecules were not yet generally national orientation. The liquefaction to mathematics got Heike to switch to accepted in those days [2]. As a student of helium opened up unexplored ter- the physicsticular department, interest led by Gustav inbecause Groningen, Kamerlingh the Onnes gradual had high as 10 T (100.000 Gauss): “An un- of electrons goes round and round and ritories of extreme cold and cleared the Kirchhoff. Important for Heike was been attracted to Van der Waals’ results path for the eventual discovery of su- that Kirchhoffincrease was a modern shows physicist, thatand to thethe kinetic electrons theory of Clausius, at 4.2 foreseen difficulty is now found in our round […] virtually without friction.” perconductivity on 8 April 1911. in the sense that he propagated the Maxwell and Boltzmann. way, but this is well counterbalanced His colleague Kuenen proposed an ex- by the discovery of the curious property periment, depicted in Fig.8, in which 04 100 years of supercondictivity 100 years of supercondictivity 05 Heikewhich Kamerlingh is the cause ofOnnes it”. the loop of lead could be interrupted, Cryostat with mercury resistor and mercury Historic plot of resistance (Ω) versus Fig.5 Fig.6 24 leads for the 26 October 1911 experiment (same temperature (K) for mercury from the 26 or even repeatedly opened and closed color scheme as in Fig. 2): seven October 1911 experiment showing the PERSISTENT CURRENTS from outside, thus forming the first U-shaped glass capillaries in series (inner superconducting transition at 4.20 K. The last notes about superconductivity (mechanical) persistent mode switch. diameter 0.07 mm), each with a mercury Within 0.01 K the resistance jumps from reservoir at the top and contact leads also made immeasurably small (less than 10 -5 Ω) in the archives are dealing with the per- Upon Ehrenfest’s suggestion Kamer- of glass capillaries filled with mercury. External to 0.1 Ω. sistent mode experiments carried out lingh Onnes repeated the experiment contacts were made through Pt wires (denoted during the spring and summer of 1914. with a single lead ring, which also by Hgxx) shown in the top right drawing. Kamerlingh Onnes concentrated on worked. Still, Kamerlingh Onnes never the question how small the resistance believed that the “micro-residual re- K were still predominantly scattered by below TC actually was and designed an sistance” was really zero, revealing that phonons (Planck vibrators). From the elegant experiment using the lead coil he was not aware of the new (quantum) sudden jump it was clear that a totally in a closed-loop configuration. When state of matter he had discovered. That new and unexpected phenomenon had this device is cooled through TC in an Fig.8 Design for the June 1914 experiment with (left) the cryostat with insert, (center) the mechani- insight came in 1933 with the experi- been discovered, which Kamerlingh applied magnetic field, any change cal persistent mode switch (superconducting “key”) with p and q lead rings, and a, b, and ments of Meissner and Ochsenfeld in c current leads and voltage leads, and (right) the cutting machine (Archive of the Museum Onnes from thereon called ‘supracon- in field will generate a current in the Boerhaave, Leiden). Berlin and the explanation by the ductivity’. closed loop which, if the resistance is young Gorter in Haarlem telling us really zero, will circulate for ever. The that a superconductor actually is a per- MATERIALS AND MAGNETS magnetic field produced by that circu- fect diamagnetic rather then a perfect An interesting entry form 20 June 1912, lating current was probed by a compass conductor, and finally in 1957 with the “Discussed with Holst ….
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