Department of Mathematics
Faculty of Natural Sciences
My life before BGU:
I was born and raised in Jerusalem (a city that is part of my identity) and attended Hebrew University High School. While in high school I competed an undergraduate degree in mathematics and computer sciences at the Hebrew University. After my army service I flirted briefly with medicine, and a bit more with bioinformatics, and eventually settled on a master’s and PhD in computer sciences, also at the Hebrew University. After completing my PhD, I spent a year as a postdoc at the Weizmann Institute while my wife completed her PhD and then we went together for a joint postdoc in Pittsburgh, PA, at Carnegie Melon University. The Coronavirus broke out soon after we arrives, so, in practice, most of my postdoc was spent working from home.
My research:
My field is the theory of computer sciences, which entails investigating the mathematical foundations of computing. One aspect of this field, in addition to researching what computers can do, is trying to understand what computers will never be capable of doing. For example, it is sometimes possible to prove that no computer built in the future will ever be able solve a certain problem, regardless of how technologically sophisticated and advanced it is.
My main sub-specialization within the theory of computer sciences is coding theory. Coding theory was developed originally to solve the following common problem: Alice is talking with Bob, but because of noise on the line, Bob cannot hear Alice clearly and he struggles to understand her. One possible solution is for Alice to repeat each sentence five times (in other words, to add redundancy to message) in the hope that Bob will be able to understand her despite the noise. The solution, unfortunately, really slows down the rate of communication. Error correcting code is a more sophisticated way of adding redundancy that allows for rapid communication across noisy channels. Coding theory attempts to develop efficient codes for a range of purposes, as well as testing inherent limitations. For example, showing that beyond a certain noise level, it is impossible to communicate efficiently no matter what code Alice and Bob use. While the original motivation behind coding theory came from the field of communication, today coding can serve different purposes in almost every sub-field in the theory of computer sciences.
Technically, code is a is a collection of “code words” that must be as different as possible from one another so that Bob does not confuse them. Code words are comparable to points in space, with two code words that are similar being like two points that are close to one another. Thus, the word ‘hello’ is close to the word ‘jello’ but far from the word ‘zebra.’ Therefore, we don’t want hello and jello to both serve as code words. This problem of finding good code words is analogous to a mathematical problem in geometry called “sphere packing.” In sphere packing, one must get as many spheres as possible of a given size into a box. For our purposes, imagine the practical problem of packing oranges for shipping so they take up as little space as possible. Similarly, we attempt to introduce as many code words as possible into the code, with each code word surrounded by a circle that does not allow for additional similar code words. The math used to analyze this problem includes tools from combinatorics, algebra, and probability.
Why BGU?
The department here seems fantastic, in both its personal and professional aspects; and very closeknit.
An insight from my research:
A common phenomenon in my field is having a problem that you have already tried to solve in twenty different ways, all of which failed. Now we are trying to solve it using the twenty-first method. Some people can just do these experiments one after the other while keeping their cool. I’m not that kind of person, so I had to adopt a different method to keep from freaking out: I simply embrace an unreasonable optimism. I start every experiment with confidence that it will succeed, and when it fails, I immediately convince myself that the next attempt is the one that will work. This demands a certain kind of mental acrobatics, but it works for me.
Something that doesn't appear on my CV:
• I’m married with a 4-year-old daughter and a 1-year-old son.
• I used to take part in amateur musical productions. And I adopted this hobby to the classroom: as a teaching assistant, Shaul Almagor (today at the Technion) and I used to perform a particularly nerdy song we wrote about our research at the end of the semester. Once, we even performed at a professional conference (watch it here)
• I coached the Israeli team for the computer sciences youth Olympiad for five years and was a contestant myself in the distant past. To any girls and boys with an interest in this, I highly recommend this wonderful endeavor. You don’t have to be a particularly good coder; mathematical thinking is much more important.
A source of inspiration:
Alan Turing, considered to be the founder the theory of computer sciences field. Beyond being a brilliant scientist, Turing became famous long after his passing as a key figure in the breaking of the German enigma encryption code during WW2. It is said he personally made a decisive contribution to the Allied victory. After the war he was persecuted by the government for being homosexual, and this eventually drove him to commit suicide in 1954. The British government apologized officially in 2009, and his portrait has appeared on the ₤50 note since 2021. I suggest skipping the Turing biopic, The Imitation Game.
When I grow up:
As a child I wanted to do many different things. One of them is precisely what I am doing today. Other professions I fantasized about were doctor (hi Dad), psychologist, and script writer.
If I wasn’t a researcher, I would...
I think I would be a doctor and psychologist. In academia, I channel my caretaking impulse into teaching.
In Brief:
» Fauda or Big Brother? Neither
» Yoga or CrossFit? Pilates. An if I must choose from the given options, then CrossFit Yoga is a bit too chill for me
» Hapoel or Maccabi? Hapoel Jerusalem. This is the easiest question on the list. Support for Maccabi would make my grandfather spin in his grave, not to mention Beitar. Hapoel Jerusalem’s soccer team has a group of fans whose values include feminism, Arab-Jewish cooperation and support for LGBTQ. In this sense, it is the best team in Israel, no question
» Ravid Plotnik or Noa Kirel? Emm… the Beatles?
» Steak or tofu? Morally, Tofu. In practice, both
» Trekking or the spa? Trekking
» Car or train? Bicycle
» Classical Europe or India? India. I’ve never been and really want to go there
» Ocean or pool? Spring. In Pittsburgh we would go to lakes and streams a lot
» Night or morning? I’m a night person, but my kids a morning people, so morning
» Winter or summer? I’m against rain and against heat, so I guess Autumn
» City or country? City, though there is a fantasy about country life
» Film or play? I really like both
» Phone call or text message? Text
» Savory or sweet? Sweet, I guess
» Android or iPhone? I have no opinion
» Cat or dog? I really like both, but am allergic to cats, so dog
» Facebook or Twitter? Twitter for news and politics. Facebook for friends
