Theoretical Nuclear Physics: Nuclear ReactionsHerman Feshbach and Ernest M. Henley Citation: Phys. Today 45(12), 84 (1992); doi: 10.1063/1.2809918 View online: http://dx.doi.org/10.1063/1.2809918 View Table of Contents: http://www.physicstoday.org/resource/1/PHTOAD/v45/i12 Published by the American Institute of Physics. Additional resources for Physics TodayHomepage: http://www.physicstoday.org/ Information: http://www.physicstoday.org/about_us Daily Edition: http://www.physicstoday.org/daily_edition

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arise elsewhere. These structures areoften capable of storing, transferringand using information. Complex sys-tems do exist in the physical world—for example, turbulent fluids or spinglasses—but much of the researchdescribed in the book focuses onadaptive systems found in the livingworld—such as the immune system orthe economy.

The time evolution of a complexsystem is often surprising and impos-sible to predict from its rules andinitial conditions. As Holland pointsout, though, the understanding to besought is not typical of conventionalscience, which strives for predictabi-lity in detail; the patterns of weatheror economics, for example, never set-tle down or repeat themselves exact-ly. One goal then is to understand thestructures that repeatedly emerge,their dynamics and how they interact.We can't, for example, predict exactlywhen a hurricane will arise, but wecan be pretty sure we'll see a few eachfall, and we have a reasonable ideaabout how they'll behave.

Throughout the sections of the bookthat attempt to present the funda-mental characteristics of complex sys-tems as understood by different indi-viduals, Waldrop achieves remark-able success in conveying theimportant ideas in a very accessiblestyle with little jargon and no equa-tions. As writers of popular scienceknow, this is no easy task.

Much of the rest of the narrativefocuses on the origins of the institute,particularly the economics program;the efforts of George Cowan, PhilAnderson, David Pines, Murray Gell-Mann, Pete Carruthers and others torealize their vision of the institute,while simultaneously trying to agreeon what that vision is; and the currentthoughts of some of its most activeresearchers as to what the futureholds. Of particular interest is thesearch for a new set of laws that willfinally elevate complexity, adaptationand emergence to something like anew thermodynamics. Needless tosay, the speculation becomes morerampant as the book proceeds; it willinfuriate some physicists, inspire oth-ers and amuse the rest—but it makesfor good reading.

Waldrop's book is clearly patternedin many ways after James Gleick'senormously successful book Chaos,and it is impossible to avoid compari-son. Gleick's is the broader book,certainly more history-minded andperhaps more objectively written.Waldrop's book in some parts comesdangerously close to hero-worship.Gleick also had the tremendous ad-vantage of writing about a subject

that had already become sharp andfocused. Most physicists, at least,knew precisely what the word chaosmeant before reading Gleick's book.

Which brings us back to the diffi-culty posed at the beginning of thereview. The sense of this book, whichI believe to be accurate, is that (atleast at the Santa Fe Institue) theredoes exist a broad consensus on thenature of complexity and the kinds ofproblems that fall under its purview.This consensus may be somewhatvague and certainly falls short ofdetailed agreement, but otherwise life(and science) would be boring. Intrying to construct a more preciseconceptual framework, one mustgrapple with an old question: Hownecessary is it for a concept to beprecisely defined before real scientificprogress can be made? Although onecan find examples that answer thequestion either way, there are cases inwhich important progress was madebased on intuition, with preciselydefined terms coming later. A widelyused example is the progress in ourunderstanding of heat and energy inthe early 19th century, as DoyneFarmer pointed out to Waldrop.

Perhaps part of the problem is thatthe term "complex," to which somewish to ascribe a scientific meaning,has a clear connotation in everydayusage. Its intended meaning is ob-scured when taken to be synonymouswith "more difficult than other prob-lems." This connotation may leadsome to perceive more than a hint ofarrogance. (One of my colleagues, ahigh-energy physics experimentalist,has posted on his door a sign reading,"Institute for Simple Systems.") Asecond difficulty for some is theaggressive interdisciplinary nature ofthe work done at the Santa Fe Insti-tute. My response is that such pur-suits are part of the lifeblood of theSanta Fe Institute and probably thefuture of science. One of the mostvaluable lessons a scientist can drawfrom Waldrop's book is that the boun-daries of our traditional disciplinesare dictated as much by history as bythe nature of the world we try tocomprehend.

Theoretical NuclearPhysics: NuclearReactions

Herman FeshbachWiley, New York, 1992. 959 pp.$150.00 he ISBN 0-471-05750-9

It is a pleasure to have a comprehen-sive book on nuclear reactions by oneof the world's foremost experts on the

subject. Theoretical Nuclear Physicsis useful for advanced graduate stu-dents and research physicists—espe-cially in nuclear physics, but also inother fields of physics—because itincludes descriptions of many-bodyreaction theory, multiple scattering,resonance theory and related topics.However, the book is not intended tocover scattering theory per se, as isdone, for instance, in the classic bookby Marvin L. Goldberger and Ken-neth Watson, Collision Theory (Wiley,New York, 1964). In his book Her-man Feshbach concentrates on tech-niques applicable to nuclear physics,particularly at energies below rough-ly 1 GeV. It is therefore a disasterthat the book has been priced beyondthe reach of most graduate studentsand that its cost will discourage physi-cists in fields outside nuclear physicsfrom purchasing it.

The richly illustrated book followsup on and complements Amos de Sha-lit and Feshbach's earlier volume,Theoretical Nuclear Physics: NuclearStructure (Wiley, New York, 1974;reprinted in paperback in 1990), andthere are numerous references to theearlier text throughout the latest one.Indeed, the two volumes belong to-gether, and the reader will find itmuch easier to digest the newertreatise if she or he has read theearlier one or has it available forreference.

The book summarizes the develop-ment of scattering theory as appliedto nuclear physics over the last 40years. It is clear that the author is inhis element when he treats suchtopics as projection operator tech-niques and doorway states, to whichhe made major contributions. That isnot to say that there are not excellentand thorough discussions of manyother topics, such as analog states,antisymmetry in direct reactions, dis-torted-wave approximations and theformalism of transfer reactions (in-cluding those in heavy-ion collisions).The text includes a chapter on heavy-ion reactions and two sections onrelativistic and ultrarelativistic colli-sions. It concludes with a chapter onpion and kaon scattering.

The author states in the introduc-tion that it is "not possible to becomplete or up to date." The empha-sis is on classical nuclear physics andmore so on topics with which theauthor is familiar through his ownresearch or that of his colleagues atMIT. Thus, some topics, such as"rainbow" scattering, are omitted,and most references are from theperiod of the development of thetheory (from roughly 1950 to 1980).Feshbach states that his goal is to give

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BOOKSsufficient background to "make thecurrent literature and review articlesaccessible to the reader." He suc-ceeds admirably in this endeavor.The downside is that there is verylittle material related to the substruc-ture of the nucleons. The book hasnumerous references to and illustra-tions of experimental results. Prob-lems do not appear at the end of eachchapter, but rather are scatteredthroughout, and they are directlyrelated to the development in thetext.

Aside from the usual misprints—not excessive—I have few quibbles. Anumber of facts are presented withoutadequate explanation. An example isthe weak spin-orbit force of the A-Ninteraction, which is mentioned earlyin the book; this spin-orbit splitting isbarely referred to in the description ofhypernuclei in the book's lastchapter. Also, in the depiction of thedouble charge exchange of pions, theexplanation of the behavior of thecross section at low energies is notgiven. There are also a very fewstatements that could be miscon-strued, such as blaming isospin non-conservation on the electromagneticinteraction and not mentioning quarkmass differences or QCD effects.

However, these are minor reserva-tions. Overall this is an excellenttreatment of the basic scattering theo-ry required to understand nuclearphysics experiments and their re-sults.

ERNEST M. HENLEYUniversity of Washington

Space SailingJerome L. WrightGordon and Breach,Philadelphia, 1992. 258 pp.$24.00 pb ISBN 2-88124-842-X

The pressure exerted by solar radi-ation on a perfectly reflecting perpen-dicular surface is about 9 X 10~6 N/m2

at 1 AU. A sail made from Kaptonfilm 2 microns thick with a 0.1-micron-thick aluminum coatingwould weigh about 3 g/m2. The accel-eration of the sail itself from lightpressure would then be about 3 mm/sec2. This is about half the accelera-tion due to the Sun's gravitationalfield.

Solar sailing was repeatedly invent-ed in the pre-Sputnik years by, forexample, Frederik Tsander, RussellSaunders and Richard Garwin.Among its potential applications arespiralling out from low Earth orbit togeosynchronous orbit in tens of daysor to escape in about 100 days. Solarsails can increase the number of

satellites that maintain a constantlongitude, which could be importantwhen geosynchronous orbits becomecrowded (as proposed by Robert L.Forward). Transporting freight andpassengers between orbits by "sailingships" could be much cheaper thanusing chemical rockets. Yet I know ofno report of any attempt to deploysolar sails in space.

In the early 1980s Jerome Wrightbecame interested in the possibility ofusing solar sailing to rendezvous withHalley's Comet during its 1986 pas-sage. This proposal was enthusiasti-cally received by the Jet PropulsionLaboratory. Wright led a group thatdeveloped solar sailing technology inconsiderable detail for this mission.The group settled on the heliogyrodesign, which looks like a huge heli-copter, with 12 rotating blades 7340meters long held out by centrifugalforce. The total surface area of theblades was 0.625 km2, and the overallweight was estimated to be 4 tonnes(about twice the weight of the simplefilm sails without the operations mod-ule or the payload). The group studiedand dealt with the problems of deploy-ment, dynamics and space environ-ment conditions (radiation, microme-teorite damage and so on). In the end,none of these hazards did them in.Space shuttle cost overruns demand-ed their funds, and NASA cancelledthe Halley rendezvous mission.

This book also reflects enthusiasmfor even more imaginative applica-tions of space sailing. Wright out-lines K. Eric Drexler's design forfabricating by vapor deposition inspace aluminum films that are twoorders of magnitude lighter than the2-micron Kapton films. He discussesForward's designs for sailing to AlphaCentauri with the aid of massivesolar-driven lasers.

It is sad that the space shuttle,which has disastrously increased thecost of going into orbit, still haspolitical power enough to displacemuch imaginative space science andengineering. Wright's book has cap-tured some of the charm and creati-vity that should be the guiding char-acteristic of our space program.

ARTHUR KANTROWITZDartmouth College

Surface Science:An Introduction

John B. HudsonButterworth-Heinemann,Boston, 1992. 321 pp.$59.95 he ISBN 0-7506-9159-X

At the 1976 March meeting of theAmerican Physical Society, Robert

Schrieffer remarked in an invitedtalk on surface physics that "if youstay in the field a while, it's a form ofmasochism to continue." While hesoon moved to one-dimensional sys-tems, the field of surface science hasthrived, even garnering two entirecategories for March meeting ab-stracts. Nonetheless, remarkably fewbooks have appeared that are suitableintroductions to the subject.

Many instructors who offer special-topics courses have adopted AndrewZangwill's Physics at Surfaces (Cam-bridge U. P., New York, 1988). WhenRobert L. Park reviewed that text inScience (30 September 1988, page1839) he lamented the short shriftgiven to many experimental tech-niques in the book's mere 450 pages.Hence, John Hudson's book—justover 300 pages long—can hardly beexpected to cover everything. And,not surprisingly, Hudson, a distin-guished experimenter, emphasizestopics on which he did research dur-ing his long tenure as a materialsengineer at Rensselaer PolytechnicInstitute. The book developed from acourse Hudson taught variously overtwo decades to graduate and ad-vanced undergraduate students inphysics, chemistry and engineering.

In some sense, because problemsappear at the end of each of its 17chapters, this is the first real textbookon surface science. (The questionstypically require the student to usethe information and formulas to gaina quantitative feel for specific sys-tems.) To hold down the book's price,Hudson himself produced the manyfigures not taken from other publica-tions. He has put an impressiveamount of time, thought and care intothis volume.

The book is divided into four parts.The first and longest provides a gen-eral introduction and deals in depthwith the thermodynamics of surfacesand surface mobility. The acknowl-edged "special debt" to John Blakely's"pioneering book," Introduction tothe Properties of Crystal Surfaces(Pergamon, Oxford, UK, 1973) is mostevident in this part. (Unfortunately,the book contains little on progresssince the early 1970s in the statisticalmechanics of surfaces. One can nowinterpret thermodynamic measure-ments in terms of microscopic inter-actions between atoms using powerfultools from statistical mechanics andcomputational physics.) The secondpart considers interactions betweengases and surfaces, with particularemphasis on beam scattering andchemical rates. In the third section,on energetic-particle probes of sur-faces, Hudson deals with the topics

PHYSICS TODAY DECEMBER 1992 8 5

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