A few minutes before 8 AM local time on Tuesday, January 12, 2010, Professor Masoud Alimohammadi, a quantum field theorist and elementary particle physicist at the University of Tehran, was assassinated outside the front door of his home by a remote-controlled bomb hidden in a parked motorbike. 
Who would want to kill this distinguished 50-year-old Iranian academic, and why?
Let us systematize our speculations under the assumption that this assassination was a political act, and not simply a murder motivated by personal factors such as revenge, jealousy or criminal activity. There is no hint that Professor Alimohammadi was anything other than he seemed: a theoretical physicist immersed in his studies and teaching, and an otherwise cultured and moderate individual unlikely to be mixed up in a criminal underworld.
So, he must have been killed because he was taken to be a symbol for the target of a political attack. What was that target?:
— the Persian academic and scientific elite, seen as too “Western” or too “secular” by domestic and atavistic fundamentalists?;
— the present regime of the Islamic Republic of Iran, attacked by radical domestic political opponents through Professor Alimohammadi as a proxy, because they are too weak to attack the high-security installations or elite political individuals of the state?; or
— the very fact of an independent-minded Shia-dominated Iranian state, attacked through the assassination proxy by foreign enemies of such a political state? 
A speculation bandied in the Western press is that Professor Alimohammadi might have been killed by the Iranian regime itself, and blamed on Israel and the United States, so as to punish the professor for his mild political dissent, and as a convenient excuse to impose a period of political repression throughout the country to suppress the unrest that erupted in June 2009 with the contested (and possibly stolen) re-election of President Mahmoud Ahmadinejad. 
This last idea is unlikely for three reasons:
(1) Professor Alimohammadi was not significantly dissident:
— he had signed a letter expressing support for the main opposition candidate, Mir Hussein Moussavi, along with 240 other university professors prior to the June election, but after it he stated publicly that he did not support the street demonstrations by Moussavi supporters;
(2) Governments can easily and unobtrusively silence politically disobedient speech by their more troublesome but still useful scientists and academics:
— with personal interventions by security officers, and limitations on career opportunities, as the United Stated did with J. Robert Oppenheimer;
— or with “internal exile” for its most troublesome scientists, like Andrei Sakharov during the 1970s and 1980s in the former Soviet Union;
— or with actual exile from paranoid and racist regimes, such as the 1955 deportation, from the McCarthy-maddened United States, of Tsien Hsue-Shen (Qian Xuesen) who went on to become the “father of the Chinese rocketry”;
— or, in extreme cases, by simple disappearance and execution, like that of Hussein Kamel (admittedly, not actually a scientist), Saddam Hussein’s son-in-law and director of weapons programs who defected from Iraq in 1995, disclosing that all Iraqi unconventional weapons — biological, chemical, missile and nuclear — had been destroyed after the First Gulf War (post 1991); before he chose to return to Iraq (being officially assured of a safe return), and oblivion;
(3) No government wishes to seed the public consciousness with doubts about its degree of control, or its ability to protect the public from foreign attack; hence they usually avoid eliminating secretly condemned dissidents by such unsettling and attention-getting methods as explosions in urban neighborhoods. It is not necessary to surreptitiously blow up a harmless professor to create an excuse for a new wave of repression; the flimsiest of excuses justified with insubstantial and secret evidence held within the ever vigilant and useful security services is always enough to reassure the patriots of the land that the new “strong measures” are essential. We are in the age where virtual Reichstag fires are enough.
The rapidity and vigor of Iranian statements in response to the assassination seem to reflect a quite genuine sense of shock and loss. That Professor Alimohammadi was an asset to the Iranian nation is evident from the rapid and prominent diffusion of the story by the Iranian state media, the rich and unstinting praise for Professor Alimohammadi issued by the Iranian government (a “committed and revolutionary” professor), and the angry accusations by that government of Israeli and U.S. culpability in the crime (“signs of the triangle of wickedness by the Zionist regime, America and their hired agents, are visible in the terrorist act”), which it viewed as an attack on the Iranian program to develop nuclear energy. Besides feeling the loss of the person and expertise of Professor Alimohammadi, the Iranian government is also stung by the embarrassment of such a flagrant breach of its internal security.
Western media accounts note that Professor Alimohammadi was an academic physicist in the highly abstract, mathematical and frontier topic of quantum field theory. He was not an applied or experimental physicist working in what is today really the engineering disciple of applying the nuclear physics of the early to mid 20th century to develop nuclear energy and nuclear weapons technology. Though objectively true that Professor Alimohammadi was not a “nuclear physicist” and his large body of published work has no bearing on the technological physics of nuclear power and nuclear weapons, it is still true that his role as an educator would have had a long-term value to Iran’s nuclear technology program: the education of young physicists who would go on to develop Iran’s nuclear technology — for peace or war.
A quantum field theory (the term is general) describes how any of the four fundamental physical forces (electromagnetic, “weak,” “strong” and gravity), or any combination of them, is maintained over a distance, even when the scale of that distance is so short, or the duration of time so brief, or the density of mass so great that quantum effects can dominate. Examples include:
— the electromagnetic binding of orbiting electrons (negatively charged particles) around the nucleus of an atom (a bound cluster of positively charged protons to charge-free neutrons) by the action of discrete, charge-free mass-less “quanta” of electromagnetic energy called photons;
— the various ways helium atoms stack when gaseous helium is cooled and liquified to nearly 273 degrees centigrade below 0 C;
— the manner in which the more elementary sub-atomic particles, like quarks and gluons (gluons are also a type of quantum), combine to form each of the well-known long-lived particles that make up atoms: electrons, protons and neutrons; (as well as more exotic forms of evanescent matter at extremely high energy, a subject of experiments at facilities like the Large Hadron Collider, the LHC).
Specific quantum field theories are used to describe the nature of specific forms of matter that exists in a condensed state, such as in a solid or liquid; and the entire field of such studies is called condensed matter physics. Professor Alimohammadi published papers in condensed matter physics. Examples of quantum effects in condensed matter include:
— the geometric arrangements of electrons and nuclei in crystals;
— the electromagnetic and electro-optical (often infra-red) responses of a semiconductor to an imposed voltage or current across it;
— the nature of the deep interiors of stars, neutron stars, and “black holes” (more in a bit);
— the nature of a quark-gluon ‘soup’ produced at the LHC by the head-on collision of two protons, each traveling at nearly the speed of light, and each propelled to a kinetic energy (energy of motion) of 7 TeV
[7 TeV = 7 thousand billion electron-volts = 1.12 micro Joules — about the energy to lift a 114 gram (4 oz.) apple one millionth of a meter off the ground; but since a proton at rest only has a mass of 1.67/(10 to the 24 power) grams, 7 TeV would lift a static proton 6.8 x (10 to the 16 power) kilometers against a constant gravity equal to that at the Earth’s surface (9.806 meters/second-squared)].
Because stars are so massive, their gravity compresses the stellar core into a ‘soup’ (or “plasma”) at least of collapsed atoms: mixed atomic nuclei, electrons and photons. With greater mass comes greater compression, at some point producing a plasma of electrons, protons, neutrons and photons. A star cools and its outward pressure drops as the energy released by nuclear fusion reactions wriggles out and is radiated away. Very massive stars may eventually compress their cores to the point of collapsing the electron, proton, neutron and photon plasma into completely neutron matter. J. Robert Oppenheimer co-authored papers on neutron stars, before WW2. The most massive stars “burning out” may ultimately collapse their cores to such high density that they become the cold quark-gluon plasma interiors of black holes, stellar remnants so massive they even bend their own light back into themselves by the action of their enormous gravitation.
Another condensed matter system that somewhat resembles a stellar interior is a compressed and radiating mass of uranium undergoing fission chain reactions; the mass heating up by its self-capture of a portion of the nuclear radiation (gamma photons and neutrons) released by nuclear fission.
The analogy to a star becomes stronger when the fissile mass resides within a metal case that also contains a balloon of mixed deuterium and tritium gases (isotopes of hydrogen). The case intercepts, re-radiates and accumulates the X-ray photon emission from the atoms of the heated interior, and the flux of radiation becomes so intense that the energy deposited on the exterior of the balloon becomes sufficient to compress it to the point of inducing deuterium-tritium fusion reactions. Some of the highly energetic neutrons emitted by fusion reactions can collide into the fissile material (splitting uranium nuclei) and significantly boost its rate of fission reaction, boosting the total yield of energy.
From these brief descriptions of nuclear bomb dynamics, the first for a fission bomb , the second for a thermonuclear bomb , it is easy to see why a theoretical physicist knowledgeable about neutron stars, J. Robert Oppenheimer, was put in charge of the scientific development of the first U.S. atomic bombs.
If Professor Alimohammadi had lived, and if Iran were to dramatically increase its uranium enrichment capability, and to also produce many kilograms of bomb grade fuel (U-235 at >90% instead of <4% mass fraction; natural uranium is 0.72% U-235), and then proceed with a bomb engineering program, then Professor Alimohammadi might have been a candidate for the Oppenheimer role in Iran; (4 conditions, one moot and three doubtful, leading to a vague possibility now negated).
The closest Professor Alimohammadi ever came to this improbable situation was to have been a professor at Imam Hossein University concurrently with his professorship in the Physics Department at Tehran University.
Imam Hossein University is a public university of engineering, applied science, and military affairs in Iran, run like a service academy (e.g., West Point, Annapolis) by the Islamic Revolutionary Guard Corps (IRGC). It is Iran’s center for the application of science and technology to military needs, and the education of scientific personnel for jobs in military institutions and industries. Imam Hossein University was organized from separate pre-existing defense programs and institutions in 1986, in the last years of the Iran-Iraq War (1980-1988), to help Iran develop domestic munitions and military technology (defense) industries. The bitter experiences of that war (Saddam Hussein’s Iraq had U.S. political and logistical support, and used chemical weapons against Iran) forged Iranian resolve to maintain an extensive and modern defense industrial complex. Imam Hossein University can be seen as the research and training center of that complex. So, it is here that critics point to as the home of presumed Iranian nuclear weapons research. 
One has the sense that Professor Alimohammadi did his ‘pure’ research and maintained his academic standing within the international theoretical physics community through his professorship at Tehran University, and that he performed his pedagogical ‘national service’ at Imam Hossein University.
Professor Alimohammadi would have taught advanced physics students at Imam Hossein University the methods of quantum field theory, and would have shown specific applications to describe quantitative models of a variety of condensed matter systems. Some of these students might go on to combine this advanced knowledge with their other engineering and computing skills to develop new computer codes to simulate complex physical problems involving highly energetic matter. “Weapons physics” is the study of energetic material phenomena for military applications; it combines experiments (as possible) and computing, with the aim of ultimately developing computational models (codes) that can guide the engineering of specific military devices. This is how nuclear weapons codes are developed.
It is quite possible to develop a nuclear weapons design code based on textbook physics and results published in the open (peer reviewed) literature; and it is equally possible to apply such a code to ‘paper’ studies (i.e., entirely virtual) of nuclear bomb designs. Astrophysicists apply this same technique to simulate stellar evolution, and interpret astrophysical observations (such as the occurrence of supernovas). To validate your theoretical bomb code, you need experimental data such as from an actual nuclear test. Real bomb codes have many ‘fudge factors’ set by the requirement of matching calculated results to actual bomb test measurements. Eventually, with enough test data, you may arrive at a reasonably reliable bomb design code.
So, it is quite possible that Iran already has some young virtual nuclear bomb designers, even if it has no nuclear bomb material and little likelihood of producing any. This possibility exists for any nation that has a physics community of comparable (and even lesser) extent and sophistication. Were such young physicists to move to a nuclear weapons state, and be given the security clearances to work as bomb designers, they would very quickly learn the trade.
The training of young Iranian defense industry physicists, and potential nuclear weapons designers, must have been Professor Alimohammadi’s capitol offense in the eyes of his executioners. He was killed to assassinate the potential of an Iranian thermonuclear bomb. Such a motivation presumes a somewhat sophisticated mind of far-reaching paranoia and obsessive pettiness, minimal humanity, a deep antipathy toward the Islamic Revolutionary Guard Corps, and probably a vaulting ambition.
So, who did it? My guess: Iranians opposed to the current regime, perhaps in one of several power-seeking groups competing for foreign sponsorship by mounting independent operations, like the killing of Professor Alimohammadi, to gain credibility. And, who could be the foreign godfathers dispensing funds, equipment, explosives and political cover? We might guess they would be the richest and/or vilest enemies of the Islamic Republic of Iran (the U.S.?, Israel?, Saudi Arabia?, …?) funneling in their disruptive ill-will through regional intermediaries and Iranian exile networks. A look at the map suggests many possibilities for smuggling a covert war into Iran; it borders (clockwise, from the west): Iraq, Turkey, Armenia, Azerbaijan, the Caspian Sea (to the north), Turkmenistan, Afghanistan, Pakistan, and (to the south) the Persian Gulf and Gulf of Oman.
Perhaps with time the essential facts will emerge through today’s knotted cloak of clashing propaganda.
I think it sad when human beings are abstracted into symbols to provide targets for political hatred. My condolences to Mansoureh Karami, the wife of Professor Masoud Alimohammadi; and my condolences to his family, friends, students and colleagues. Many of you lifetime physics students will understand that the essential value to physics study is not in its technological applications — though such pursuits can be very captivating, and some quite humanitarian — but in the sense of wonder one gains by seeing a bit deeper into the wondrous workings of this amazing universe. That sense can be unifying and humanizing, despite the transient cultural and political divides of the day.
Manuel García, Jr. is a retired engineering physicist (I did okay in a graduate school quantum mechanics course), had a job in U.S. nuclear testing (1978-2007), and can be reached at firstname.lastname@example.org (I don’t know any “secrets”).