Seminars and Events: Fall 2013


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  • August 2013
  • Joint DISCOVERY-HET Seminar

    Aud. A, Thursday 8 Aug at 14:15

    Rajamani Narayanan (Florida International University)

    Phase structure of two-dimensional QED at zero temperature with flavor-dependent chemical potentials and the role of multidimensional theta functions

    Joint DISCOVERY-HET Seminar

    Rajamani Narayanan


    Phase structure of two-dimensional QED at zero temperature with flavor-dependent chemical potentials and the role of multidimensional theta functions


    Abstract:


    We consider QED on a two-dimensional Euclidean torus with $f$ flavors of massless fermions and flavor-dependent chemical potentials. The dependence of the partition function on the chemical potentials is reduced to a $(2f-2)$-dimensional theta function. At zero temperature, the system can exist in an infinite number of phases characterized by certain values of traceless number densities and separated by first-order phase transitions. Furthermore, there exist many points in the $(f-1)$-dimensional space of traceless chemical potentials where two or three phases can coexist for $f=3$ and two, three, four or six phases can coexist for $f=4$. We conjecture that the maximal number of coexisting phases grows exponentially with increasing $f$.

    Details

    Date: Thursday 8 Aug

    Time: 14:15

    Place: Aud. A

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  • Conference: Current Themes in High Energy Physics and Cosmology

    NBI, Sunday 11 Aug - Monday 19 Aug at

    Current Themes in High Energy Physics and Cosmology

    Conference: Current Themes in High Energy Physics and Cosmology


    Current Themes in High Energy Physics and Cosmology


    Abstract:




    More info: https://indico.nbi.ku.dk/conferenceDisplay.py?confId=536

    Details

    Date: Sunday 11 Aug - Monday 19 Aug

    Time:

    Place: NBI

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  • NBIA Colloquium

    Aud. A, Tuesday 20 Aug at 14:15

    Itamar Procaccia (Weizmann Institute of Science)

    Numbers in Nature, Art and Architecture

    NBIA Colloquium

    Itamar Procaccia


    Numbers in Nature, Art and Architecture


    Abstract:


    In this lecture I will review the evolution of the concept of numbers in the ages as they appear in language, in Nature, in Art and in Architecture.

    Details

    Date: Tuesday 20 Aug

    Time: 14:15

    Place: Aud. A

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  • Joint DISCOVERY-HET Seminar

    Aud. A, Thursday 29 Aug at 14:15

    Alessandro Strumia (CERN)

    Naturalness after LHC Run 1

    Joint DISCOVERY-HET Seminar

    Alessandro Strumia


    Naturalness after LHC Run 1


    Abstract:


    LHC results did not confirm the theoretical expectations based on naturalness. We summarize the present status of this issue, and explore the possibility that the usual criterion for naturalness by ignoring the uncomputable power divergences.

    Details

    Date: Thursday 29 Aug

    Time: 14:15

    Place: Aud. A

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  • September 2013
  • Niels Bohr Lecture

    Aud. 3 @ HCØ, Wednesday 4 Sep at 16:15

    Subir Sarkar

    Connecting inner space & outer space

    Niels Bohr Lecture

    Subir Sarkar


    Connecting inner space & outer space


    Abstract:


    We have just celebrated the centenary of the finding that the Earth is being constantly bombarded by high energy `cosmic rays' from space. This initiated a glorious era of discovery of many new particles (positron, muon, pion, ...) and developed into accelerator-based research into high energy physics. A century later this has given us the triumphant `Standard Model' of particle physics which provides a precise quantum description of all fundamental processes in terrestrial laboratories, including (with the recent discovery of "a Higgs boson") an understanding of how particles acquire mass.

    Unfortunately the Standard Model does not explain any of the salient features of the universe as a whole - Why there is matter but no antimatter? Why there is so much more `dark matter' of unknown origin? Why is the expansion rate apparently accelerating, as if driven by a Cosmological Constant-like, dominant component of `dark energy'?

    In this lecture I will describe how new kinds of experiments and theoretical developments at the rapidly growing interface of astro-particle physics are attempting to answer these cosmic questions, by linking them to possible new physics that lies beyond the Standard Model.

    More info: http://www.nbi.ku.dk/Besoeg_os/niels_bohr_lectures/2013/subir_sarker/

    Details

    Date: Wednesday 4 Sep

    Time: 16:15

    Place: Aud. 3 @ HCØ

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  • Joint DISCOVERY-HET Seminar

    Aud. A, Tuesday 10 Sep at 14:15

    Agnese Bissi

    Higher spin correlators

    Joint DISCOVERY-HET Seminar

    Agnese Bissi


    Higher spin correlators


    Abstract:


    In this talk I will discuss the three-point correlator of two protected scalar operators and one higher spin twist-two operator in N = 4 SYM, in the limit of large spin. This structure constant can be extracted from the OPE of the four-point correlator of protected scalar operators. Based on the OPE structure, symmetry arguments and intuition from the available perturbative results, it is possible to predict the structure constant at all loops in perturbation theory. This allows also to propose an expression for the all loops four-point correlator in a particular limit.

    Details

    Date: Tuesday 10 Sep

    Time: 14:15

    Place: Aud. A

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  • Joint DISCOVERY-HET Seminar

    Aud. A, Thursday 12 Sep at 14:15

    Johannes Broedel (ETH Zurich)

    Polylogarithms, Multiple Zeta Values, Worldsheet Integrals and the Drinfeld Associator

    Joint DISCOVERY-HET Seminar

    Johannes Broedel


    Polylogarithms, Multiple Zeta Values, Worldsheet Integrals and the Drinfeld Associator


    Abstract:


    Open-string tree-level amplitudes have been calculated from worldsheet integrals using a variety of techniques during the last decades. I am going to discuss, how polylogarithms can be employed to formalize the calculation, which in turn allows to calculate those amplitudes for any multiplicity and to any order in the inverse string tension. Starting from these results, I will describe an S-matrix shortcut: employing algebraic methods utilizing the Drinfeld associator, all tree-level open-string amplitudes can be obtained recursively without solving a single worldsheet integral.

    Details

    Date: Thursday 12 Sep

    Time: 14:15

    Place: Aud. A

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  • PhD defense

    Aud. A, Friday 13 Sep at 10:00

    Martin Hansen

    Anomalies of the Cosmic Microwave Background

    PhD defense

    Martin Hansen


    Anomalies of the Cosmic Microwave Background


    Abstract:




    More info: http://het.nbi.dk/Events/13b/PHD-Hansen.html

    Details

    Date: Friday 13 Sep

    Time: 10:00

    Place: Aud. A

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  • MSc defense

    Aud. A, Tuesday 17 Sep at 11:00

    Morten H. Christensen

    Aspects of Lifshitz Holography

    MSc defense

    Morten H. Christensen


    Aspects of Lifshitz Holography


    Abstract:


    In recent years, extensions of the AdS/CFT correspondence have opened up the possibility of studying condensed matter systems using holography. Here we will consider z = 2 Lifshitz spacetimes in 4 dimensions as possible duals of 3-dimensional non-relativistic condensed matter systems exhibiting anisotropic scaling, and construct a framework in which the sources can be identied and the vevs calculated. The basis for this construction will be the fact that z = 2 Lifshitz spacetimes in 4 dimensions are related to AlAdS spacetimes by Scherk-Schwarz reduction.
    In the defense, I will briey review the holographic principle and its rst realization, namely the AdS/CFT correspondence. I then proceed to discuss the dimensional reduction of 5-dimensional AdS spaces and show that this leads to 4-dimensional Lifshitz spaces. The constraints imposed such that the 4-dimensional theory is Asymptotically locally Lifshitz are reviewed and I argue that a deformation is required in order to calculate the vevs of the boundary theory. Various irrelevant deformations are considered and new classes of spacetimes, namely the generalized AlLif and Lifshitz UV, are dened. It is shown that the
    boundary geometry of these spacetimes is that of Newton{Cartan with torsion. Furthermore, we dene ALif spacetimes whose boundary geometry is pure Newton{Cartan. Within the Lifshitz UV spacetime the sources of the 4-dimensional theory are analyzed. Due to the consistency of the reduction, the 4-dimensional vevs can be written entirely in terms of the 5-dimensional vevs. This fact is used to calculate the stress-energy tensor of the boundary theory. Furthermore, we nd six Ward identities constraining the vevs of the boundary theory and use these to argue for a definition of a gauge invariant stress-energy tensor.

    More info: http://het.nbi.dk/Events/13b/MSc-Christensen.html

    Details

    Date: Tuesday 17 Sep

    Time: 11:00

    Place: Aud. A

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  • Discovery Colloquium

    Aud A, Tuesday 17 Sep at 14:15

    Veronica Sanz (Sussex)

    The Higgs is here, and now what?

    Discovery Colloquium

    Veronica Sanz


    The Higgs is here, and now what?


    Abstract:


    In this colloquium we will discuss the recent discovery of the Higgs particle. We will review the current understanding of its properties, and the prospects of using Higgs data to learn about new principles in Nature. We will explain how Supersymmetry, new strong dynamics, and other proposals for beyond the Standard Model can be probed making use of this data. We will finish with an overview of what is the next frontier in the experimental Higgs program.

    Details

    Date: Tuesday 17 Sep

    Time: 14:15

    Place: Aud A

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  • Joint HET-Discovery seminar

    Aud A, Thursday 19 Sep at 14:15

    David Skinner (Cambridge)

    Twistor Strings for N=8 Supergravity

    Joint HET-Discovery seminar

    David Skinner


    Twistor Strings for N=8 Supergravity


    Abstract:


    I'll explain a new way of looking at 4d supergravity --- as a theory of holomorphic maps into Penrose's twistor space. Allowing twistor space to have N fermionic directions, the theory is anomaly free when N=8. Via the Penrose transform, the vertex operators correspond to an N=8 Einstein supergravity multiplet. Conformal symmetry is explicitly broken by the presence of the infinity twistor in the BRST operator. The complete classical S-matrix is recovered from worldsheet correlation functions and interpreted geometrically. Time permitting, I will explain what I know of the model at higher genus.

    Details

    Date: Thursday 19 Sep

    Time: 14:15

    Place: Aud A

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  • Two-minute meeting

    Aud. A , Tuesday 24 Sep at 14:15

    Two-minute meeting



    Abstract:




    More info: http://het.nbi.dk/Events/13b/twominute2013.html

    Details

    Date: Tuesday 24 Sep

    Time: 14:15

    Place: Aud. A

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  • Niels Bohr Lecture

    Aud. 3 @ HCØ, Wednesday 25 Sep at 15:15

    Priyamvada Natarajan (Yale University)

    From seeds to behemoths: tracking the formation of supermassive black holes in the universe

    Niels Bohr Lecture

    Priyamvada Natarajan


    From seeds to behemoths: tracking the formation of supermassive black holes in the universe


    Abstract:


    Populations of quasars powered by accretion onto SMBHs with masses in excess of 10^9 solar masses are now detected when the Universe was barely a Gyr old. And in the local universe the centers of several nearby brightest cluster galaxies harbor behemoths that weigh ~ a few times 10^10 solar masses.

    I will discuss how these monster black holes likely form and what observational signatures can test the various formation & growth scenarios. Aside from outlining the current status of our understanding, I will close with the open exciting questions and challenges ahead for theory given the wealth of observational data in hand and in the pipeline.


    More info: http://www.nbi.ku.dk/Besoeg_os/niels_bohr_lectures/2013/priyamvada_natarajan2/

    Details

    Date: Wednesday 25 Sep

    Time: 15:15

    Place: Aud. 3 @ HCØ

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  • Joint DISCOVERY-HET Seminar

    Aud. A, Thursday 26 Sep at 14:15

    Claudio Pica (CP3-Origins, University of Southern Denmark)

    Studies of Minimal Walking Technicolor on the lattice

    Joint DISCOVERY-HET Seminar

    Claudio Pica


    Studies of Minimal Walking Technicolor on the lattice


    Abstract:


    Minimal Walking Technicolor (MWT) models have been proposed to explain the mechanism for Electroweak symmetry breaking by replacing the fundamental Higgs particle with a new strongly interacting sector, in which the Higgs is composite. In view of the recent discovery of the Higgs particle and the experimental searches for MWT by the ATLAS collaboration, it is relevant to understand MWT models quantitatively in more detail. I will present some of our recent lattice studies of two MWT models, the SU(2)a and the SO(4)v models, aimed at determining the details of the strong dynamics and provide inputs for the experimental searches.

    Details

    Date: Thursday 26 Sep

    Time: 14:15

    Place: Aud. A

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  • October 2013
  • HET journal club lunch

    Fb-6, Wednesday 2 Oct at 12:30

    Start-up meeting

    HET journal club lunch


    Start-up meeting


    Abstract:




    Details

    Date: Wednesday 2 Oct

    Time: 12:30

    Place: Fb-6

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  • HET journal club seminar

    Fb-6, Wednesday 2 Oct at 13:15

    Gianluca Grignani

    Thermal DBI at weak and strong coupling

    HET journal club seminar

    Gianluca Grignani


    Thermal DBI at weak and strong coupling


    Abstract:




    Details

    Date: Wednesday 2 Oct

    Time: 13:15

    Place: Fb-6

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  • PhD Defense

    Aud. A, Thursday 3 Oct at 14:00

    Jakob Gath

    Hydrodynamics and Elasticity of Charged Black Branes

    PhD Defense

    Jakob Gath

    Supervisor: Niels Obers


    Hydrodynamics and Elasticity of Charged Black Branes


    Abstract:


    We consider long-wavelength perturbations of charged black branes to first order in a fluid-elastic derivative expansion. At first order the perturbations decouple and we treat the hydrodynamic and elastic perturbations separately. To put the results in a broader perspective, we present the first-order corrected dynamics of fluid branes carrying higher-form charge by obtaining the general form of their equations of motion to pole-dipole order in the absence of external forces. To monopole order, we characterize the corresponding effective theory of viscous fluid branes by writing down the general form of the first-order dissipative corrections in terms of the shear and bulk viscosities as well as the transport coefficient associated with charge diffusion. To dipole order, we furthermore, applying linear response theory, characterize the corresponding effective theory of stationary bent charged (an)isotropic fluid branes in terms of two sets of response coefficients, the Young modulus and the piezoelectric moduli.

    We subsequently consider a large class of examples in gravity of this effective theory. In particular, we consider dilatonic black p-branes in two different settings: charged under a Maxwell gauge field and charged under a (p+1)-form gauge field, including the D-branes and M-branes of type II string theory and M theory, respectively. Using familiar techniques, we compute the associated transport coefficients and uncover how the shear and bulk viscosities are modified in the presence of electric charge and a dilaton coupling. For the case of Maxwell black branes we furthermore compute the charge diffusion constant. We find that the shear viscosity to entropy bound is saturated and comment on proposed bounds for the bulk viscosity to entropy ratio. With the transport coefficients we compute the first-order dispersion relations of the effective fluid and analyze the dynamical stability of the black branes.

    We then focus on constructing stationary strained charged black brane solutions to first order in a derivative expansion. Using solution generating techniques and the bent neutral black brane as a seed solution, we obtain a class of charged black brane geometries carrying smeared Maxwell charge in Einstein-Maxwell-dilaton theory. In the specific case of ten-dimensional space-time we furthermore use T-duality to generate bent black branes with higher-form charge, including smeared D-branes of type II string theory. We compute the bending moment and the electric dipole moment which these solutions acquire due to the strain and uncover that their form is captured by classical electroelasticity theory. In particular, we find that the Young modulus and the piezoelectric moduli of the strained charged black brane solutions are parameterized by a total of four response coefficients, both for the isotropic as well as for the anisotropic cases.

    Details

    Date: Thursday 3 Oct

    Time: 14:00

    Place: Aud. A

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  • MSc defense

    Aud. A, Friday 4 Oct at 13:00

    Therkel A. Zøllner Olesen

    Twisted mass Wilson chiral perturbation theory

    MSc defense

    Therkel A. Zøllner Olesen


    Twisted mass Wilson chiral perturbation theory


    Abstract:




    Details

    Date: Friday 4 Oct

    Time: 13:00

    Place: Aud. A

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  • HET journal club lunch

    Fb-6, Wednesday 9 Oct at 12:30

    HET journal club lunch



    Abstract:




    Details

    Date: Wednesday 9 Oct

    Time: 12:30

    Place: Fb-6

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  • Joint DISCOVERY-HET Seminar

    Aud. A, Thursday 10 Oct at 14:15

    Alessandro Codello

    Fluctuating (Fluid) Membranes

    Joint DISCOVERY-HET Seminar

    Alessandro Codello


    Fluctuating (Fluid) Membranes


    Abstract:


    Fluid membranes are d-dimensional re-parametrization invariant hyper-surfaces embedded in a D-dimensional target space. When d=2 and D=3, they are used as a model for real physical systems in biophysics and in soft-condensed matter. Recently, they have been used to model generalized Galileon theories; in this case D=d+1.
    After introducing functional Renormalization Group methods, I'll show how these can be applied to fluctuating membranes to obtain their phase diagram for general values of d and D.
    Finally I'll propose a possible connection between fluctuating membranes (where both extrinsic and intrinsic curvatures are present) and quantum gravity (where only intrinsic curvature is present).


    Details

    Date: Thursday 10 Oct

    Time: 14:15

    Place: Aud. A

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  • NBIA Colloquium

    Aud A, Friday 11 Oct at 14:30

    Jan Heinemeier

    How accelerators, carbon-14 and stable isotopes reveal news of past and present: Age of archaeological materials, tissue and wine

    NBIA Colloquium

    Jan Heinemeier


    How accelerators, carbon-14 and stable isotopes reveal news of past and present: Age of archaeological materials, tissue and wine


    Abstract:


    I will give an overview of how levels of carbon 14 measured by
    Accelerator Mass Spectrometry and stable isotopes can answer a wide
    range of questions, such as:
    -How old are archaeological findings?
    -What did the Vikings eat?
    -How fast is turnover of human tissue?
    -Is your expensive Barolo wine actually from 1998?

    Details

    Date: Friday 11 Oct

    Time: 14:30

    Place: Aud A

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  • HET journal club seminar

    Fb-6, Wednesday 23 Oct at 13:15

    Thomas Vanel (LPTHE)

    Dressing the electron star in a holographic superconductor

    HET journal club seminar

    Thomas Vanel


    Dressing the electron star in a holographic superconductor


    Abstract:


    Over the last five years, the gauge/gravity correspondence has been applied to describe quantum critical systems at finite density. The simplest model to consider is Einstein-Maxwell gravity, and the ground state of the system is described by Reissner-Nordstrom black hole where all the charge is carried by the black hole. However, it turns out that this solution is unstable to the formation of both fermionic and bosonic matter, corresponding in the dual field theory to the creation of a Fermi surface and the onset of superconductivity, respectively. We consider Einstein-Maxwell system coupled to a perfect fluid of charged fermions and a charged scalar field. In addition to the black hole, electron star and holographic superconductor solutions, we find new asymptotically AdS4 solutions, dual to 2+1 CFTs at zero temperature and finite chemical potential, which contain both scalar hair and an electron star. We compute the free energy and show that these new solutions are thermodynamically favoured when they exist. Moreover, we find evidence for a continuous phase transition between the holographic superconductor and the new solutions.

    Details

    Date: Wednesday 23 Oct

    Time: 13:15

    Place: Fb-6

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  • Niels Bohr Lecture

    Aud 3 @ HCØ, Wednesday 23 Oct at 15:15

    Achim Rosch (Universität zu Köln)

    Magnetic whirls in chiral magnets: skyrmions and monopoles

    Niels Bohr Lecture

    Achim Rosch


    Magnetic whirls in chiral magnets: skyrmions and monopoles


    Abstract:


    In chiral magnets and small magnetic fields lattices of magnetic whirls, so-called skyrmions, can be stabilized. These skyrmions can be manipulated by electric currents which are 5-6 orders of magnitude smaller than conventionally needed for the manipulation of magnetic structures. The very efficient coupling of the magnetic structure to currents is governed by Berry phases, which can be described by effective "emergent" electromagnetic fields. The topological quantization of the the skyrmions thereby leads to a quantization of the emergent magnetic flux. A change of topology has to occur by singular magnetic configurations [3] which act as sources and sinks of the emergent magnetic flux. Thereby they can be viewed as emergent magnetic monopols.

    More info: http://www.nbi.ku.dk/Besoeg_os/niels_bohr_lectures/2013/achim_rosch/

    Details

    Date: Wednesday 23 Oct

    Time: 15:15

    Place: Aud 3 @ HCØ

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  • Joint Discovery-HET Seminar

    Aud A, Thursday 24 Oct at 14:15

    Jacopo Ghiglieri (McGill)

    Higher-order calculations of hard probes in the quark-gluon plasma

    Joint Discovery-HET Seminar

    Jacopo Ghiglieri


    Higher-order calculations of hard probes in the quark-gluon plasma


    Abstract:


    At sufficiently high temperatures and vanishing chemical potential QCD exhibits a crossover to a deconfined phase, the quark-gluon plasma, which is probed in heavy-ion collision experiments. Hard probes, i.e. highly energetic, off-equilibrium particles (photons, dileptons, jets), are of particular relevance in this investigation. In my talk I will discuss in detail the calculation of the thermal photon rate, which has recently been completed to next-to-leading order. I will show how Euclidean and sum rule techniques can be introduced and how this advancement renders the calculation simpler than expected. Finally, I will show how similar techniques can be applied to deal with highly energetic partons and jets.

    Details

    Date: Thursday 24 Oct

    Time: 14:15

    Place: Aud A

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  • Joint DISCOVERY-HET Seminar

    Aud. A, Tuesday 29 Oct at 14:15

    Subodh Patil (CERN)

    Correlating features in the primordial specta, or, how do we know it really was an inflaton?

    Joint DISCOVERY-HET Seminar

    Subodh Patil


    Correlating features in the primordial specta, or, how do we know it really was an inflaton?


    Abstract:


    CMB and matter density field observations derive from n-point correlation functions of the comoving curvature perturbation R. As far as we can tell, all observations to date are consistent with the predictions of the simplest models of single-field slow roll inflation. However, if all we have access to are observations of correlators of adiabatic perturbations, one infers limited information as to what the background was actually doing. Degeneracies and dualities are known to exist between differing backgrounds that result in the same 2-point correlators, which begs a host of operational questions: how do we know whether or not inflation really happened? What is the true nature of the inflaton? How does it embed itself in a sector that also contains the standard model?

    In this talk I will review how the purported common lore `smoking gun' signatures of inflation are anything but, and demonstrate that one possible way to infer that inflation really happened would be to observe a hierarchy of correlations between the different n-point correlators of R. These correlations are a direct consequence of the effective field theory expansion of R, which non-linearly realizes the breaking of time translational invariance by slow roll. The observation of such correlations in the n-point spectra over a range of e-folds would directly confirm the nature of inflaton as an effectively single light scalar degree of freedom embedded in a theory that is UV completable, and is the consequence of transient stronger couplings of certain operators in the effective theory as inflation progresses. We discuss the prospects for observing such correlations in future LSS and 21cm observations.

    Details

    Date: Tuesday 29 Oct

    Time: 14:15

    Place: Aud. A

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  • HET journal club lunch

    Fb-6, Wednesday 30 Oct at 12:30

    HET journal club lunch



    Abstract:




    Details

    Date: Wednesday 30 Oct

    Time: 12:30

    Place: Fb-6

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  • Joint DISCOVERY-HET Seminar

    Aud. A, Thursday 31 Oct at 14:15

    Jacob Sonnenschein (Tel Aviv University)

    Holographic Stringy Hadrons

    Joint DISCOVERY-HET Seminar

    Jacob Sonnenschein


    Holographic Stringy Hadrons


    Abstract:


    I will briefly review the stringy holographic calculation of Wilson lines and the sufficient conditions for confining ones. I will show that these are also the conditions to have a Regge-like holographic stringy mesons. I will show that classically the latter can be mapped into rotating strings in flat space-time with massive endpoints. I will determine the massive modification of the Classical Regge trajectories. The issues associated with the quantization of such strings will be briefly reviewed. I will present fits of the modified trajectories to the experimental data of mesons starting from $\rho$ and $w$ mesons and all the way to $b\bar b$ mesons. The best fit values of the string tension, the intercept and the string endpoint masses will be presented. I will present the computation of the decay width of the holographic stringy mesons and their relation to the CNN and Lund models. I will describe the holographic stringy baryons including the location of the baryonic vertex and possible structures of such baryons. The stability of Y shape baryons will be discussed. Fits of holographic Regge trajectories to Nucleons and other baryons will be described. I will present arguments in favor of the picture of a single string with quark on one hand and a baryonic vertex and a di-quark in the other hand.

    Details

    Date: Thursday 31 Oct

    Time: 14:15

    Place: Aud. A

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  • November 2013
  • NBIA Colloquium

    Aud A, Friday 1 Nov at 14:15

    Roger Penrose (University of Oxford)

    Twistor Theory and Basic Physics: Some Recent New Ideas

    NBIA Colloquium

    Roger Penrose


    Twistor Theory and Basic Physics: Some Recent New Ideas


    Abstract:


    Twistor theory was initiated in 1963 as an alternative description of
    space-time physics, based fundamentally on the complex number system,
    and dependent on crucial links with the formalism of quantum theory.
    Despite many developments, little attention was paid to it until 40
    years later, when Edward Witten pointed out significant connections with
    the calculation of high-energy scattering processes. Important later
    work by many researchers, including Andrew Hodges and Nima Arkani-Hamed
    have developed the theory in novel directions, all this leading to vast
    simplifications in the calculation of scattering amplitudes. Much of
    this activity is in the direction of perturbation analysis, early work
    on exact solutions of the non-linear Einstein and Yang–Mills equations
    having been hampered by being restricted to just one helicity by the
    so-called “googly problem”. A novel approach to circumventing this
    difficulty will be presented.

    Details

    Date: Friday 1 Nov

    Time: 14:15

    Place: Aud A

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  • Discovery-HET Seminar

    Aud A, Tuesday 5 Nov at 14:15

    Chad Finley

    Evidence for High Energy Astrophysical Neutrinos Seen by IceCube

    Discovery-HET Seminar

    Chad Finley


    Evidence for High Energy Astrophysical Neutrinos Seen by IceCube


    Abstract:


    The IceCube Neutrino Observatory, built deep within the glacial ice at the South Pole, Antarctica, became fully operational in 2011. This unique instrument allows the study of a wide range of phenomena, from dark matter searches to neutrino oscillations to cosmic ray physics. Analyses using the first year of data from the completed detector have revealed strong evidence of high energy neutrinos reaching Earth from distant space. Among these are the two highest energy neutrinos ever observed. Making a definitive measurement of this extraterrestrial flux will be a major advance toward the century-old goal of identifying and studying the origins of high energy cosmic rays. In this talk, I will review recent highlights, and discuss the latest results and their analysis, which have also turned conventional thinking about neutrino telescopes upside down.

    Details

    Date: Tuesday 5 Nov

    Time: 14:15

    Place: Aud A

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  • HET journal club lunch

    Fb-6, Wednesday 6 Nov at 12:30

    HET journal club lunch



    Abstract:




    Details

    Date: Wednesday 6 Nov

    Time: 12:30

    Place: Fb-6

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  • HET journal club seminar

    Fb-6, Wednesday 13 Nov at 13:15

    Yegor Korovin (University of Amsterdam)

    On the field theory dual to Lifshitz space

    HET journal club seminar

    Yegor Korovin


    On the field theory dual to Lifshitz space


    Abstract:



    We consider holography for Lifshitz spacetimes with dynamical exponent z=1+epsilon^2, where epsilon is small. ?he holographically dual field theory is a specific deformation of the relativistic CFT, corresponding to the z=1 theory. We set up the holographic dictionary for Einstein-Proca models and explain how renormalization turns the relativistic conformal invariance into non-relativistic Lifshitz invariance with dynamical exponent z=1+epsilon^2. Using only QFT arguments we show that a particular class of deformations of CFTs generically leads to Lifshitz scaling invariance and we provide examples of such deformations. An analytic Lifshitz black brane up to second order in e is constructed. Relation to some top-down construction will be discussed. Based on 1304.7776 and 1306.3344.

    Details

    Date: Wednesday 13 Nov

    Time: 13:15

    Place: Fb-6

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  • Discovery-HET Seminar

    Aud M, Thursday 14 Nov at 14:15

    Noboru Kawamoto (Hokkaido University)

    Current Status of Exact Supersymmetry on the Lattice

    Discovery-HET Seminar

    Noboru Kawamoto


    Current Status of Exact Supersymmetry on the Lattice


    Abstract:


    I will explain the fundamental difficulties of lattice
    supersymmetry in an introductory way and then review
    two of our proposals to solve these difficulties.
    I will mainly focus on the basic ideas of the formulations.

    Details

    Date: Thursday 14 Nov

    Time: 14:15

    Place: Aud M

    View in Google Calendar

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  • Discovery-HET Seminar

    Aud A, Tuesday 19 Nov at 14:15

    Matti Jarvinen

    Holographic models for QCD in the Veneziano limit

    Discovery-HET Seminar

    Matti Jarvinen


    Holographic models for QCD in the Veneziano limit


    Abstract:


    I discuss holographic bottom-up models for QCD in the Veneziano limit
    (large N_f and N_c with fixed x=N_f/N_c). I will start by giving and
    introduction to the topic and by reviewing earlier work. Then I will go
    on discussing a specific class of models, named V-QCD. The models are
    constructed by putting together holographic models of Yang-Mills theory
    (improved holographic QCD) with Sen-type tachyon actions inspired by
    brane constructions, and by considering full backreaction. The resulting
    phase diagrams and mass spectra meet expectations from QCD at
    qualitative level.

    Details

    Date: Tuesday 19 Nov

    Time: 14:15

    Place: Aud A

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  • HET journal club lunch

    Fb-6, Wednesday 20 Nov at 12:30

    HET journal club lunch



    Abstract:




    Details

    Date: Wednesday 20 Nov

    Time: 12:30

    Place: Fb-6

    View in Google Calendar

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  • Joint Discovery-HET Seminar

    Aud A, Thursday 21 Nov at 14:15

    Ciaran Williams (NBIA & Discovery Center)

    Bounding the Higgs width at the LHC

    Joint Discovery-HET Seminar

    Ciaran Williams


    Bounding the Higgs width at the LHC


    Abstract:



    I will discuss the potential for the LHC to constrain the Higgs width.
    At the LHC direct measurement of the width is impossible for
    widths smaller than the detector resolution (of around 1 GeV).
    Therefore an alternate approach is employed in which the
    width is constrained from off-shell H=>ZZ events. I will
    present an overview of the method, including the analytic calculation
    of gg=>ZZ using D-dimensional unitarity. I will then discuss
    the potential improvements on the limits if Matrix Element
    Methods are employed in the analysis.


    Details

    Date: Thursday 21 Nov

    Time: 14:15

    Place: Aud A

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  • HET journal club seminar

    Fb-6, Wednesday 27 Nov at 13:15

    Shahar Hadar (Hebrew University)

    An action for reaction: an effective field theory study of post-Newtonian radiative effects

    HET journal club seminar

    Shahar Hadar


    An action for reaction: an effective field theory study of post-Newtonian radiative effects


    Abstract:


    We present an effective field theory (EFT) describing radiation and radiation-reaction effects in the post-Newtonian approximation of General Relativity. Our formulation allows a unified treatment of outgoing radiation and its reaction force within an action formalism, and significantly economizes extant derivations. New results on radiation and reaction in general spacetime dimensions, obtained within our EFT, will be presented. In particular, the difference between even and odd spacetime dimensions in our context will be discussed. Finally, we will comment on the availability of a similar EFT treatment for near-extremal black holes.

    Details

    Date: Wednesday 27 Nov

    Time: 13:15

    Place: Fb-6

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  • Discovery-HET Seminar

    Aud. A, Thursday 28 Nov at 14:15

    Rutger Boels

    Constructing the string S-matrix in target space

    Discovery-HET Seminar

    Rutger Boels


    Constructing the string S-matrix in target space


    Abstract:


    String theory is a theory of strings amongst many other things. The usual way of describing string theory is therefore through its world-sheet. This however always involves an enormous amount of, in principle, redundant information. A simple question is: can string theory be defined without this redundancy? Based on joint, very-soon-to-appear work with Tobias Hansen I'll show a working definition of tree level string theory in a flat target space. We have a small-ish set of conditions in target space whose unique solution is argued to be the usual string S-matrix. Interestingly, the notions of critical dimension and intercept are shown to arise naturally by requiring locality and unitarity. I'll end with more questions than answers, but at least the questions are interesting and well-posed. In particular there seem to be no fundamental restrictions to generalize to curved spaces.

    Details

    Date: Thursday 28 Nov

    Time: 14:15

    Place: Aud. A

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  • December 2013
  • HET journal club seminar

    Bk-2, Tuesday 3 Dec at 11:30

    Niall Macpherson (Swansea)

    Non-abelian T-duality and Holography

    HET journal club seminar

    Niall Macpherson


    Non-abelian T-duality and Holography


    Abstract:


    My talk will be based on recent developements in non-abelian T-duality as a solution generating technique with applications to holography. I will start with a pedagogical review of T-duality along SU(2) isometries and then narrow my focus to dualising type-II SuGra solutions dual to QFTS with minimal SUSY. I will give several explicit examples where I will probe gauge theory dynamics, some inherited from the original solution some from the large number of fluxes typically generated by the duality. Along the way I will introduce generalised geometry into the narrative as this gives an elegant classification of the T-dual geometries in terms of g-structures and enables an extension of the duality to include calibrated sources, with clear applications to holography with smeared flavours. In addition one can show, quite generally, that in 6-d the duality maps SU(3) to SU(2). The dual structure is actually dynamical SU(2) whenever the original solution is confining.

    Details

    Date: Tuesday 3 Dec

    Time: 11:30

    Place: Bk-2

    View in Google Calendar

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  • HET journal club lunch

    Fb-6, Wednesday 4 Dec at 12:30

    HET journal club lunch



    Abstract:




    Details

    Date: Wednesday 4 Dec

    Time: 12:30

    Place: Fb-6

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  • HET journal club seminar

    Fb-6, Wednesday 11 Dec at 11:15

    Oluf Tang Engelund (Penn State)

    Generalized Unitarity for 2D Integrable Models

    HET journal club seminar

    Oluf Tang Engelund


    Generalized Unitarity for 2D Integrable Models


    Abstract:


    Generalized unitarity is a powerful method for doing perturbative calculations. I will discuss how to apply it to worldsheet S-matrices for the Green Schwarz string in curved space. The studied theories are believed to be integrable to all orders in perturbation theory and symmetries have been used to determine exact S-matrices up to an overall dressing phase. Generalized unitarity can provide a simple way to check the proposed S-matrices perturbatively and to find dressing phases. I will give some 1- and 2-loop examples and touch upon some of the potential challenges that may arise at higher loop orders.

    Details

    Date: Wednesday 11 Dec

    Time: 11:15

    Place: Fb-6

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  • Discovery-HET Seminar

    Aud A, Wednesday 11 Dec at 14:15

    Christoph Englert (University of Glasgow)

    The Higgs Sector Quest

    Discovery-HET Seminar

    Christoph Englert


    The Higgs Sector Quest


    Abstract:


    After the discovery of the Higgs boson in 2012, the importance of
    reaching a better understanding of the nature of the electroweak scale
    has become more important and more central to Particle Physics than
    ever. I will discuss examples of how to improve and complement current
    measurement strategies through exploiting new analysis techniques and
    BSM interference effects in SM processes. The described programme not
    only provides an opportunity to phenomenologically gain insights into
    the mechanism of electroweak symmetry breaking itself, but also allows
    to establish a "no-hide" theorem for natural extensions of the SM.

    Details

    Date: Wednesday 11 Dec

    Time: 14:15

    Place: Aud A

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    ×
  • HET journal club lunch

    Fb-6, Wednesday 18 Dec at 12:30

    HET journal club lunch



    Abstract:




    Details

    Date: Wednesday 18 Dec

    Time: 12:30

    Place: Fb-6

    View in Google Calendar

    ×