Strings ante portas
Tomorrow Strings 2008 kick off here at CERN. The place and the timing of the conference were carefully planned to coincide with the first LHC results that would hint toward string theory. The plan didn't quite work out due to the LHC schedule slip, which means we have to wait one more year for the ultimate confirmation of string theory. The expectation makes it all even more exciting.
The warm-up for Strings 2008 was the Summer Institute on String Phenomenology that has been taking place at CERN TH during the last month. Although I'm usually attracted by wordplay, puns and oxymorons, this time I didn't manage to attend many talks. That's partly due to my summer travelling, and partly due to my summer paresse. Among the few talks I've seen I best remember the one by Cumrun Vafa who talked about F-theory phenomenology. He presented a simple and elegant construction that connects F-theory to reality (that is to the MSSM). Although I wasn't able to grasp all the details, the picture below gives a rough idea: 
For detailed experimental predictions, the experimentalists from ATLAS and CMS are encouraged to consult this paper. Although there are no specific predictions for the superparticle spectrum, your perspective may be changed by the fact that the Higgs particle you will discover is in reality a matter curve on Riemann surfaces located at the intersection between the
GUT model seven-brane and additional seven-branes in the full compactification where the U(1) hypercharge flux is non-vanishing. For the neutrino physicists, the important piece of information is that the neutrinos are Dirac or Majorana and their masses are roughly of the order of what is observed. I heard some skeptics saying that back in the old days phenomenology meant a different thing, but such grumbling should not be taken seriously.
Highlights from the conference along with more nasty comments are soon to appear on this blog. Live webcast here or via technically more advanced Lubos' blog.
16 comments:
I want tenure so I can make posts like this....
Dear Compatriot,
If you really want to see some experimental predictions, then you should look here:
http://arxiv.org/abs/0808.0497
You can see how low string mass can nullify the landscape and anthropic nonsense.
Did Vafa mention the paper by Saulina et. al where they took Vafa's setup and constructed a model with gauge-mediated susy breaking arXiv:0808.1571[hep-th]?
It looks like they were able to derive the "Sweet spot SUSY" scenario which is very intriguing. Don't you think?
It is probably interesting from the string-model-building point of view. What I wanted to say is that what matters from the phenomenological point of view is the superparticle spectrum. For that purpose, the field theoretical framework (gauge mediation, in the case you quote) is fully sufficient, and the F-theory approach does not provide any new piece of information.
I don't complain about F-theory model building - I do complain about claiming relevance for phenomenology.
Till now, the most spectacular thing is the display of portables from the audience (to which I contribute my iRex and an Aspire One)
(Also funny, the problems on the speaker side, to project the slides)
I agree that gauge mediated SUSY breaking mechanism is captured by a field theoretic approach, no question about it. But there are thousands of models with gauge mediated SUSY breaking with all kinds of adhoc assumptions. The detailed properties of the messenger sector as well as the hidden and visible sectors such as mass scales, allowed and forbidden couplings, etc, cannot be apriory determined just from field theory. In the paper I mentioned, Saulina et al explicitely relied on the F-theory construction to determine some of those properties. So, you cannot just say that there was no new piece of information from F-theory.
the susy breaking scale in the F-theory models is arbitrary and not determined by the model. It has to be, it is sourced by an instanton and the amplitude of the instanton comes from the closed string sector whose dynamics are not considered.
the most the paper says is that the amplitude of the instanton can be consistent with having a 1GeV gravitino. which one may say is another kind of adhoc assumption.
Sure, the scale of m_{3/2} is not completely determined. However, the form of the superpotential is completely determined by the underlying geometry which, among other things, forbids the generation of the B\mu term and sets the scale of \mu to be that of the SUSY breaking scale as opposed to the GUT scale. The fact that the corresponding geometry gives a SUSY GUT with no exotics and simultaneously addresses other problems such as the doublet-triplet splitting, the supersymmetric CP problem etc. is very non-trivial in my opinion.
Certainly the models have something interesting. In particular, the matter content is nice. But let's not get carried away. The gravitino mass is undetermined. The geometry has nothing to do with the susy CP problems (if this is solved here by anything, it is solved by the mediation mechanism - gauge mediation is a field theory mechanism and not an string theory one.) Various fields which are both local and dynamical (e.g. the instanton amplitude) have been frozen. Make them dynamical, and they will give runaway.
Don't get me wrong, it is good that people work on this. But it is also good to be spared claims that suddenly F-theory has solved all open problems in phenomenology (which was the impression I got reading the second long paper, YMMV...)
note the F-saga follows in arXiv:0806.0102 "Experimental Predictions". It is interesting that they "require that any viable model contain precisely three
generations of chiral matter".
Ibañez also adds some other teams (besides UAM, of course) actually having models with three generations:
Donagi, Ovrut, Faraggi,... but to me it seems a bit ad-hoc, to choose Z2 or Z3 to quotient, without further classification theorems to apply.
Honestly, HEP theory does not help very much to select a mechanism for generations. The only hint, told by Faraggi (I believe. Or was it Ovrut?) time ago, is that we need a given number of fermions to hit the meeting of couplings in GUT running. Well, there is also that another hint from mine: the sBootstrap of SU(5) flavour. But it is only group theory (yet).
Another hint I thought last week: if you take seriusly that the yukawa of the top is the only natural one, the other put to zero, then you can consider the limit of infinite mass for W and Z. In this limit, the neutrinos *and the top* decouple, while the gauge group reduces to SU(3)xU(1). But it means that we have a sort of generation-less scenario, and the 24 fermions of the standard model (counting antiparticles, so one 4-component fermion for each yukawa parameter) have reduced to 18.
Strings has failed spectacularly. Why the bullshit? Return to physics, my degree subject, where experiment rules, not self-denial rubblish. Strings is embarrassing a noble subject.
WoW shares many wow gold of its features with previously launched games. Essentially, you battle with wow gold cheap monsters and traverse the countryside, by yourself or as a buy cheap wow gold team, find challenging tasks, and go on to higher aoc gold levels as you gain skill and experience. In the course of your journey, you will be gaining new powers that are increased as your skill rating goes up. All the same, in terms of its features and quality, that is a ture stroy for this.WoW is far ahead of all other games of the genre the wow power leveling game undoubtedly is in a league of its own and cheapest wow gold playing it is another experience altogether.
Even though WoW is a Cheap Wow Gold rather complicated game, the controls and interface are done in warhammer gold such a way that you don't feel the complexity. A good feature of the game is that it buy wow items does not put off people with lengthy manuals. The instructions bygamer cannot be simpler and the pop up tips can help you start playing the game World Of Warcraft Gold immediately. If on the other hand, you need a detailed manual, the instructions are there for you to access. Buy wow gold in this site,good for you, BUY WOW GOLD.
Making habbo credits
is the old question : Honestly there is no fast way to make lots of habbo gold. Sadly enough a lot of the people that all of a sudden come to with millions of habbo coinsalmost overnight probably duped . Although there are a lot of ways to make lots of cheap habbo credits here I will tell you all of the ways that I know and what I do to buy habbo gold.
Weekends to peopleig2tmean that they can have a two-day wowgold4europe good rest. For example， people gameusdcan go out to enjoy themselves or get meinwowgoldtogether with relatives and friends to talk with each storeingameother or watch interesting video tapes with the speebiewhole family.
Everyone spends agamegoldweekends in his ownmmoflyway. Within two days,some people can relax themselves by listening to music， reading novels，or watchingogeworld films. Others perhaps are more active by playing basketball，wimming ormmorpgvipdancing. Different people have different gamesavorrelaxations.
I often spend weekends withoggsalemy family or my friends. Sometimes my parents take me on a visit to their old friends. Sometimesgamersell I go to the library to study or borrow some books tommovirtexgain much knowledge. I also go to see various exhibition to broadenrpg tradermy vision. An excursion to seashore or mountain resorts is my favorite way of spending weekends. Weekends are always enjoyable for me.
igxe swagvaultoforu wowgold-usaignmax wowgoldlivebrogame thsaleGoldRockU
網頁設計,網頁設計公司,最新消息,訪客留言,網站導覽
情趣用品,情趣用品,情趣用品
色情遊戲,寄情築園小遊戲,情色文學,一葉情貼圖片區,情人視訊網,辣妹視訊,情色交友,成人論壇,情色論壇,愛情公寓,情色,舊情人,情色貼圖,色情聊天室,色情小說,做愛,做愛影片,性愛
免費視訊聊天室,aio交友愛情館,愛情公寓,一葉情貼圖片區,情色貼圖,情色文學,色情聊天室,情色小說,情色電影,情色論壇,成人論壇,辣妹視訊,視訊聊天室,情色視訊,免費視訊,免費視訊聊天,視訊交友網,視訊聊天室,視訊美女,視訊交友,視訊交友90739,UT聊天室,聊天室,豆豆聊天室,尋夢園聊天室,聊天室尋夢園,080聊天室,080苗栗人聊天室,女同志聊天室,上班族聊天室,小高聊天室
AV,AV女優
視訊,影音視訊聊天室,視訊交友
視訊,影音視訊聊天室,視訊聊天室,視訊交友,視訊聊天,視訊美女,視訊辣妹,免費視訊聊天室
自慰器,自慰器
101煙火,煙火批發,煙火工廠,製造浪漫煙火小舖,煙火小舖,衣蝶,衣蝶,情趣用品,情趣商品,情趣,情趣,衣蝶情趣精品百貨,衣蝶情趣精品百貨,煙火批發,情趣禮品,成人用品,T字褲,按摩棒,情趣內衣,情趣精品,情趣商品,情趣用品,情趣,情趣,真愛密碼情趣用品,真愛密碼,真愛密碼,真愛密碼情趣用品,貓裝,自慰器,性感內褲,角色扮演,丁字褲,,跳蛋,AV,丁字褲,煙火,情趣用品,情趣用品
Post a Comment