Triangle Seminars
December 2005
Wed
14 Dec 2005
Towards a Holographic Description of QCD
📍 London
Nick Evans
(Southampton)
Abstract:
We review AdS/CFT Correspondence constructions of non-supersymmetric theories and include quarks using D7 brane probes. Such geometries provide a geometric decription of chiral symmetry breaking in the pattern of QCD. The
meson masses of the theory can be computed and include a pion-like goldstone boson. Phenomenological models of QCD in this spirit surprisingly work at the 10-15 percent level. Finally we address a major concern with such models - they have strongly coupled UV physics. We use ideas from perfect lattice actions to suggest a solution and show a toy example of the method in action.
We review AdS/CFT Correspondence constructions of non-supersymmetric theories and include quarks using D7 brane probes. Such geometries provide a geometric decription of chiral symmetry breaking in the pattern of QCD. The
meson masses of the theory can be computed and include a pion-like goldstone boson. Phenomenological models of QCD in this spirit surprisingly work at the 10-15 percent level. Finally we address a major concern with such models - they have strongly coupled UV physics. We use ideas from perfect lattice actions to suggest a solution and show a toy example of the method in action.
Posted by: KCL
Wed
14 Dec 2005
Towards Mirror Symmetry on (Generalized) Complex Geometries
Tetsuji Kimura
(KIAS)
Mon
12 Dec 2005
Generalized Holonomy for String and M-theory corrected spacetimes
Kelly Stelle
(Imperial College)
Mon
12 Dec 2005
Geometry, the MSSM and Searching for Evidence of New Physics
James Gray
(Durham)
Fri
9 Dec 2005
Worldline approach to vector and antisymmetric tensor fields
📍 London
Fiorenzo Bastianelli
(Bologna)
Abstract:
We study the quantization on the torus of the N=2 spinning particle
coupled to spacetime gravity to obtain a worldline representation
of the effective action of an arbitrary antisymmetric tensor field.
This representation contains on top of the usual proper time a new
modular parameter implementing the reduction to a single tensor field.
Then we describe how to use it: (i) to calculate the first few
Seeley-DeWitt coefficients for antisymmetric tensor fields of arbitrary
rank in arbitrary dimensions, (ii) to derive exact duality relations,
and (iii) to compute some correlation functions.
We study the quantization on the torus of the N=2 spinning particle
coupled to spacetime gravity to obtain a worldline representation
of the effective action of an arbitrary antisymmetric tensor field.
This representation contains on top of the usual proper time a new
modular parameter implementing the reduction to a single tensor field.
Then we describe how to use it: (i) to calculate the first few
Seeley-DeWitt coefficients for antisymmetric tensor fields of arbitrary
rank in arbitrary dimensions, (ii) to derive exact duality relations,
and (iii) to compute some correlation functions.
Posted by: KCL
Wed
7 Dec 2005
Exploring the M-theory effective action
📍 London
Michael Green
(DAMTP)
Abstract:
This talk will survey recently deduced features of the ten-dimensional
effective action for four gravitons in type II string theories. Duality
with M-theory together with supersymmetry leads to a number of
nontrivial higher derivative four-graviton interactions whose
non-perturbative structure is completely determined by a collection of
Poisson equations on moduli space and is consistent
with data provided by string perturbation theory.
This talk will survey recently deduced features of the ten-dimensional
effective action for four gravitons in type II string theories. Duality
with M-theory together with supersymmetry leads to a number of
nontrivial higher derivative four-graviton interactions whose
non-perturbative structure is completely determined by a collection of
Poisson equations on moduli space and is consistent
with data provided by string perturbation theory.
Posted by: KCL
Wed
7 Dec 2005
Supersymmetric Non-linear Sigma Models and Generalized Complex Geometry
📍 London
Ulf Lindstrom
(Uppsala)
Tue
6 Dec 2005
Random matrix theory and symmetric spaces
Ulrika Magnea
(Turin)
Abstract:
We define some elementary concepts concerning the description
of random matrix ensembles in terms of symmetric spaces.
We also discuss examples of how the mapping to symmetric spaces
can be used in some physical contexts in which a random matrix
description is applied.
We define some elementary concepts concerning the description
of random matrix ensembles in terms of symmetric spaces.
We also discuss examples of how the mapping to symmetric spaces
can be used in some physical contexts in which a random matrix
description is applied.
Posted by: KCL
Mon
5 Dec 2005
Cosmological Aspects of Loop Quantum Gravity
Johannes Brunnemann
(AEI Potsdam)
Abstract:
One main reason to quantize gravity is the hope that the singularities of classical General Relativity will be absent within the framework of a quantum theory of gravity. One candidate for such a theory is the well developed framework of Loop Quantum Gravity. During the last years remarkable results concerning the big bang singularity have been achieved within symmetry reduced cosmological models of Loop Quantum Cosmology. In this talk we will address the question whether these results are characteristic also for the full, unreduced theory. As a first step towards answering that question we will present an explicit analysis of the geometric operator corresponding to the classical inverse scale factor occurring in cosmological models which has been performed within the full theory. The results will be discussed.
One main reason to quantize gravity is the hope that the singularities of classical General Relativity will be absent within the framework of a quantum theory of gravity. One candidate for such a theory is the well developed framework of Loop Quantum Gravity. During the last years remarkable results concerning the big bang singularity have been achieved within symmetry reduced cosmological models of Loop Quantum Cosmology. In this talk we will address the question whether these results are characteristic also for the full, unreduced theory. As a first step towards answering that question we will present an explicit analysis of the geometric operator corresponding to the classical inverse scale factor occurring in cosmological models which has been performed within the full theory. The results will be discussed.
Posted by: KCL
Mon
5 Dec 2005
Higher Spin Gauge Theories and Unfolded Dynamics
Misha Vasiliev
(Lebedev Institute)
Abstract:
I review the structure of higher spin gauge theories in various dimensions, with some emphasize on the infinite-dimensional higher spin symmetries and unfolded dynamics approach. If I have time, I would also discuss how this approach works in the standard field theories like Yang-Mills and Einstein gravity.
I review the structure of higher spin gauge theories in various dimensions, with some emphasize on the infinite-dimensional higher spin symmetries and unfolded dynamics approach. If I have time, I would also discuss how this approach works in the standard field theories like Yang-Mills and Einstein gravity.
Posted by: IC
Fri
2 Dec 2005
Conjectures in modular representation of finite groups
Shigeo Koshitani
(Chiba University, Japan)
Abstract:
For the abstract follow this link: http://www.staff.city.ac.uk/c.korff/citysem.html
For the abstract follow this link: http://www.staff.city.ac.uk/c.korff/citysem.html
Posted by: CityU
Thu
1 Dec 2005
Aspects of Gauge-String Duality
Carlos Nunez
(Swansea)
Thu
1 Dec 2005
Holographic decays of large-spin mesons
Marija Zamaklar
(Max Planck)
Abstract:
I will discuss the decay process of large-spin mesons in the context of the gauge-string duality, using generic properties of confining backgrounds and systems with flavour branes. In the string picture, meson decay corresponds to the quantum-mechanical process in which a string rotating on the IR wall.
fluctuates, touches a flavour brane and splits into two smaller strings. This process automatically
encodes flavour conservation as well as the Zweig rule. I will show that the decay width computed in the
string picture is in remarkable agreement with the decay width obtained using the phenomenological Lund
model.
I will discuss the decay process of large-spin mesons in the context of the gauge-string duality, using generic properties of confining backgrounds and systems with flavour branes. In the string picture, meson decay corresponds to the quantum-mechanical process in which a string rotating on the IR wall.
fluctuates, touches a flavour brane and splits into two smaller strings. This process automatically
encodes flavour conservation as well as the Zweig rule. I will show that the decay width computed in the
string picture is in remarkable agreement with the decay width obtained using the phenomenological Lund
model.
Posted by: IC
November 2005
Wed
30 Nov 2005
What is the phase structure of N=4 SYM theory?
📍 London
Sean Hartnoll
(DAMTP)
Abstract:
I will review recent results at strong and weak coupling
in N=4 SYM theory at finite temperature. I will point out that retarded correlators have a qualitatively different analytic structure in the weak a strong coupling limits and will argue that this either necessitates a phase transition in the theory or requires that we revise our current understanding of weakly coupled plasmas.
I will review recent results at strong and weak coupling
in N=4 SYM theory at finite temperature. I will point out that retarded correlators have a qualitatively different analytic structure in the weak a strong coupling limits and will argue that this either necessitates a phase transition in the theory or requires that we revise our current understanding of weakly coupled plasmas.
Posted by: KCL
Tue
29 Nov 2005
Integrability in QCD and beyond
Gregory Korchemsky
(Universite Paris-Sud)
Mon
28 Nov 2005
Kahler-Ricci flow
Gang Tian
(Princeton University)
Abstract:
The Kahler-Ricci flow provides a useful method of deforming any Kahler metric towards a caononical metric. In this talk, we will discuss on recent progress on the Kahler-Ricci
flow and how the flow behaves on manifolds with positive Kodaira dimension and without Kahler-Einstein metrics.
The Kahler-Ricci flow provides a useful method of deforming any Kahler metric towards a caononical metric. In this talk, we will discuss on recent progress on the Kahler-Ricci
flow and how the flow behaves on manifolds with positive Kodaira dimension and without Kahler-Einstein metrics.
Posted by: IC
Fri
25 Nov 2005
Topological Strings and Large N Phase Transitions
Michele Cirafici
(Edinburgh)
Thu
24 Nov 2005
The Library of Babel: On the origin of gravitational thermodynamics
Vishnu Jejjala
(Durham)
Thu
24 Nov 2005
What is the Phase Structure of N=4 SYM Theory?
Sean Hartnoll
(DAMTP)
Wed
23 Nov 2005
Spinorial Geometry and the Heterotic String
📍 London
George Papadopoulos
(King's College London)
Wed
23 Nov 2005
–- CANCELLED –- CANCELLED –-
📍 London
Michael Green
(DAMTP)
Wed
23 Nov 2005
Quantum-to-classical crossover of quasi-bound states and fractal Weyl laws in ballistic open systems
Henning Schomerus
(Lancaster University)
Abstract:
The escape out of open quantum systems can be characterised by quasibound states, which are solutions of the wave equation subject to outgoing boundary conditions. The energy eigenvalue of a quasibound state is complex, and the imaginary part is associated to the decay rate of the state. Quasibound states can be observed, e.g., as the lasing modes of optical microresonators. Random-matrix theory gives a wealth of information on quasibound states in disordered media, such as random dielectrics. Interesting systems are, however, ballistic (clean), and scattering only takes place at the (often complicated) confinements. I discuss the similarities and differences between quasibound states in disordered and ballistic systems. A semiclassical analysis reveals that ballistic systems feature a set of quasibound states which decay very quickly (faster even than the classical time of flight). The remaining long-lived quasibound states obey random-matrix statistics, just as in disordered systems, but renormalized in compliance with a recently proposed fractal Weyl law. I illustrate these results numerically for a model system, the open kicked rotator.
The escape out of open quantum systems can be characterised by quasibound states, which are solutions of the wave equation subject to outgoing boundary conditions. The energy eigenvalue of a quasibound state is complex, and the imaginary part is associated to the decay rate of the state. Quasibound states can be observed, e.g., as the lasing modes of optical microresonators. Random-matrix theory gives a wealth of information on quasibound states in disordered media, such as random dielectrics. Interesting systems are, however, ballistic (clean), and scattering only takes place at the (often complicated) confinements. I discuss the similarities and differences between quasibound states in disordered and ballistic systems. A semiclassical analysis reveals that ballistic systems feature a set of quasibound states which decay very quickly (faster even than the classical time of flight). The remaining long-lived quasibound states obey random-matrix statistics, just as in disordered systems, but renormalized in compliance with a recently proposed fractal Weyl law. I illustrate these results numerically for a model system, the open kicked rotator.
Posted by: CityU
Tue
22 Nov 2005
Commuting Position and Momentum Operators and Emergent Classicality
Jonathan Halliwell
(Imperial College)
Abstract:
Inspired by an old idea of von Neumann, we seek a pair of commuting operators X,P which are, in a specific sense, 'close' to the canonical non-commuting position and momentum operators, x,p. Difficulties with von Neumann's original idea (involving an alleged orthogonalization of the coherent states) are discussed. Here these difficulties are avoided by restricting attention to operators acting on density matrices which are reasonably decohered (i.e., spread out in phase space). Such operators could be of use in discussions of emergent classicality from quantum mechanics. Moreover, they may be
used to give a discussion of the relationship between exact and approximate decoherence in the decoherent histories approach to quantum theory.
Inspired by an old idea of von Neumann, we seek a pair of commuting operators X,P which are, in a specific sense, 'close' to the canonical non-commuting position and momentum operators, x,p. Difficulties with von Neumann's original idea (involving an alleged orthogonalization of the coherent states) are discussed. Here these difficulties are avoided by restricting attention to operators acting on density matrices which are reasonably decohered (i.e., spread out in phase space). Such operators could be of use in discussions of emergent classicality from quantum mechanics. Moreover, they may be
used to give a discussion of the relationship between exact and approximate decoherence in the decoherent histories approach to quantum theory.
Posted by: IC
Tue
22 Nov 2005
Complex eigenvalues of the Dirac operator in two color QCD
Elmar Bittner
(Leipzig)
Abstract:
We analyze the eigenvalue spectrum of the staggered Dirac matrix
in two-color QCD at nonzero chemical potential when the
eigenvalues become complex. The quasi-zero modes and their role for
chiral symmetry breaking and the deconfinement transition are examined.
The bulk of the spectrum and its relation to quantum chaos is considered.
A comparison with predictions from random matrix theory is presented.
We further provide first evidence that matrix models describe the low lying
complex Dirac eigenvalues in a theory with dynamical fermions at nonzero
chemical potential. Lattice data for two-color QCD with staggered fermions
are compared to detailed analytical results from matrix models in the corresponding
symmetry class, the complex chiral symplectic ensemble. They confirm the predicted
dependence on chemical potential, quark mass and volume.
We analyze the eigenvalue spectrum of the staggered Dirac matrix
in two-color QCD at nonzero chemical potential when the
eigenvalues become complex. The quasi-zero modes and their role for
chiral symmetry breaking and the deconfinement transition are examined.
The bulk of the spectrum and its relation to quantum chaos is considered.
A comparison with predictions from random matrix theory is presented.
We further provide first evidence that matrix models describe the low lying
complex Dirac eigenvalues in a theory with dynamical fermions at nonzero
chemical potential. Lattice data for two-color QCD with staggered fermions
are compared to detailed analytical results from matrix models in the corresponding
symmetry class, the complex chiral symplectic ensemble. They confirm the predicted
dependence on chemical potential, quark mass and volume.
Posted by: KCL
Mon
21 Nov 2005
On the Sasaki Einstein – gauge theory correspondence
Sergio Benvenuti
(Scuola Normale Superiore Pisa)
Fri
18 Nov 2005
Five-brane Calibrations and Fuzzy Funnels
Neil Copland
(DAMTP)
Thu
17 Nov 2005
The Topological G_2 String
Jan de Boer
(Amsterdam)
Thu
17 Nov 2005
ADHM-Nahm construction re-derived from string theory
Koji Hashimoto
(Tokyo Univ.)
Wed
16 Nov 2005
Generalized Holonomy for String and M-theory corrected spacetimes
📍 London
Kellogg Stelle
(Imperial)
Wed
16 Nov 2005
Spectral properties of random manifold ensembles
John Wheater
(Oxford University)
Abstract:
The propagation of particles in random backgrounds is of interest from several points of view. Disordered media is one but my own originates in discretized quantum gravity. I will discuss some of the background and the motivation for this. Recently there has been considerable progress in obtaining essentially exact results for some problems of this type. The methods are actually very simple and intuitive and I'll explain how they work. Finally there are of course many open problems still and I'll close with them.
The propagation of particles in random backgrounds is of interest from several points of view. Disordered media is one but my own originates in discretized quantum gravity. I will discuss some of the background and the motivation for this. Recently there has been considerable progress in obtaining essentially exact results for some problems of this type. The methods are actually very simple and intuitive and I'll explain how they work. Finally there are of course many open problems still and I'll close with them.
Posted by: CityU
Tue
15 Nov 2005
Oscillating Neutrinos in Heaven and Earth
Maria Concepcion Gonzalez Garcia
(SUNY Stony Brook and Universitat de Valencia)
Abstract:
In this talk I will describe the phenomenology associated with
neutrino oscillations and I will review the evidence for neutrino mass
from solar and atmospheric neutrino experiments, as well as from the most
important laboratory searches for neutrino oscillations. I will also
briefly discuss the main implications for theory.
In this talk I will describe the phenomenology associated with
neutrino oscillations and I will review the evidence for neutrino mass
from solar and atmospheric neutrino experiments, as well as from the most
important laboratory searches for neutrino oscillations. I will also
briefly discuss the main implications for theory.
Posted by: IC
Mon
14 Nov 2005
Numerical Calabi-Yau metrics and projective geometry
Simon Donaldson
(Imperial College)
Thu
10 Nov 2005
Brane Inflation and Moduli Stabilization with Quantum Corrections
Michael Haack
(Munich)
Wed
9 Nov 2005
Mutation-selection models of sequence evolution in population genetics
Uwe Grimm
(The Open University)
Abstract:
In my talk, I shall present results that have been obtained in collaboration with Tini Garske, on mutation-selection models which describe the evolution of two- or four-letter sequences. Mutation is modelled as a Markov process, and selection is introduced via a fitness function, which assigns a reproductive fitness to each sequence. We consider permutation-invariand fitness functions, or, more generally, Hopfield-type fitness functions, where the fitness is determined by the overlap with a number of given reference sequences. For infinite sequence length, the equilibrium properties of the sequence space models can be determined from a simple maximum principle, which also proves to be a good approximation for the case of finite sequence length.
In my talk, I shall present results that have been obtained in collaboration with Tini Garske, on mutation-selection models which describe the evolution of two- or four-letter sequences. Mutation is modelled as a Markov process, and selection is introduced via a fitness function, which assigns a reproductive fitness to each sequence. We consider permutation-invariand fitness functions, or, more generally, Hopfield-type fitness functions, where the fitness is determined by the overlap with a number of given reference sequences. For infinite sequence length, the equilibrium properties of the sequence space models can be determined from a simple maximum principle, which also proves to be a good approximation for the case of finite sequence length.
Posted by: CityU
Wed
9 Nov 2005
Probing bulk spacetime with CFT correlators
Veronika Hubeny
(Durham)
Wed
9 Nov 2005
New aspects of generalized geometry
Nigel Hitchin
(Oxford)
Tue
8 Nov 2005
Black holes and extra dimensions
Harvey Reall
(University of Nottingham)
Abstract:
The decade 1963-1973 is sometimes referred to as the 'golden age' of black hole
research. Mathematical theorems proved in this period led to a complete
classical description of equilibrium black holes in four space-time dimensions.
More recently, string theory has forced us to take seriously the possibility of
extra spatial dimensions. Thinking about black holes in more than four
dimensions has led to spectacular advances in our understanding of quantum
gravity. In the last five years, we have learned that higher-dimensional black
holes exhibit much richer behaviour than four-dimensional ones, even
classically. I shall review the discoveries of this new 'silver age' of black
hole research. The talk should be accessible to MSc students.
The decade 1963-1973 is sometimes referred to as the 'golden age' of black hole
research. Mathematical theorems proved in this period led to a complete
classical description of equilibrium black holes in four space-time dimensions.
More recently, string theory has forced us to take seriously the possibility of
extra spatial dimensions. Thinking about black holes in more than four
dimensions has led to spectacular advances in our understanding of quantum
gravity. In the last five years, we have learned that higher-dimensional black
holes exhibit much richer behaviour than four-dimensional ones, even
classically. I shall review the discoveries of this new 'silver age' of black
hole research. The talk should be accessible to MSc students.
Posted by: IC
Mon
7 Nov 2005
Stringy corrections to spacetime superpotentials
Eric Sharpe
(Utah University)
Wed
2 Nov 2005
On the higher spin - gauge theory correspondence
📍 London
Paul Heslop
(DAMTP)
Wed
2 Nov 2005
Q-operator and separation of variables for the Calogero-Sutherland model
Evgeny Sklyanin
(University of York)
Abstract:
Baxter's Q-operator is the quantum counterpart of the Baecklund transformation from the theory of classical Hamiltonian integrable systems. The Q-operator, which depends on a complex parameter called spectral, shares common eigenfunctions with the Hamiltonians of a quantum integrable system and satisfies a differential or difference equation in the spectral parameter. Using the Calogero-Sutherland model as an example we shall discuss the construction of the Q-operator and comment on its application for the separation of variables.
Baxter's Q-operator is the quantum counterpart of the Baecklund transformation from the theory of classical Hamiltonian integrable systems. The Q-operator, which depends on a complex parameter called spectral, shares common eigenfunctions with the Hamiltonians of a quantum integrable system and satisfies a differential or difference equation in the spectral parameter. Using the Calogero-Sutherland model as an example we shall discuss the construction of the Q-operator and comment on its application for the separation of variables.
Posted by: CityU
Wed
2 Nov 2005
Conformal Invariance, Orbifold Field Theories and Closed String Tachyons
Radu Roiban
(Princeton)
October 2005
Mon
31 Oct 2005
Twistor String Theory
Lionel Mason
(Oxford)
Fri
28 Oct 2005
Noncommutative Spacetimes and Unitary Quantum Physics
Thupil Govindarajan
(Institute of Mathematical Sciences, Chennai, India)
Thu
27 Oct 2005
Higher spin symmetry breaking in AdS-CFT
Fabio Riccioni
(Cambridge)
Thu
27 Oct 2005
Dimer Models and Gauge Theories
Bo Feng
(IC)
Wed
26 Oct 2005
Marginal Deformations and Penrose Limits with Continuous Spectrum
📍 London
Toni Mateos
(Imperial)
Abstract:
Lunin and Maldacena recently found a simple method to generate AdS_5
supergravity backgrounds dual to exactly marginal deformations of SCFTs.
In the first part of the talk, we will consider extensions to AdS_4
backgrounds, concentrating on those for which dual IR 3d field theories
have been proposed. In the second part, we will concentrate on the
deformation of N=4 SYM in 4d and analyze a certain Penrose limit. We will
be led to consider a 'modified Landau problem' and relate it to the
different set of chiral operators of the deformed N=4.
Lunin and Maldacena recently found a simple method to generate AdS_5
supergravity backgrounds dual to exactly marginal deformations of SCFTs.
In the first part of the talk, we will consider extensions to AdS_4
backgrounds, concentrating on those for which dual IR 3d field theories
have been proposed. In the second part, we will concentrate on the
deformation of N=4 SYM in 4d and analyze a certain Penrose limit. We will
be led to consider a 'modified Landau problem' and relate it to the
different set of chiral operators of the deformed N=4.
Posted by: KCL
Wed
26 Oct 2005
S-matrix theory of laser-induced nonsequential double ionization
Carla Figueira de Morisson Faria
(City University)
Abstract:
The abstract is available at
http://www.staff.city.ac.uk/c.korff/citysem.html
The abstract is available at
http://www.staff.city.ac.uk/c.korff/citysem.html
Posted by: CityU
Mon
24 Oct 2005
Singularities of special Lagrangian submanifolds
Dominic Joyce
(Oxford)
Thu
20 Oct 2005
MHV-Vertices for Gravity Amplitudes
Harald Ita
(Swansea)
Thu
20 Oct 2005
Marginal Deformations of Tree-level N=4 SYM from Twister String Theory
Costas Zoubos
(QMW)
Wed
19 Oct 2005
10-forms in 10-dimensional supergravity theories
📍 London
Fabio Riccioni
(Cambridge, DAMTP)
Abstract:
The IIB supersymmetry algebra in d=10 can be extended including 10-forms. One of these is the RR 10-form, which takes part in the tadpole cancellation mechanism of the type-I string. D9-branes are electrically charged with respect to this 10-form. IIB supergravity possesses a global
SL(2,R) symmetry, which the quantum theory breaks to SL(2,Z). Even if 10-forms have no dynamics, since their field-strength vanishes identically, it is possible to study their behaviour under SL(2,Z) transformations. We determine all the possible independent 10-forms as representations of
SL(2,Z), and in particular we show in which multiplet the RR 10-form lies. Finally, we perform the same analysis for the IIA supersymmetry algebra, and interpret the results in terms of T-duality.
The IIB supersymmetry algebra in d=10 can be extended including 10-forms. One of these is the RR 10-form, which takes part in the tadpole cancellation mechanism of the type-I string. D9-branes are electrically charged with respect to this 10-form. IIB supergravity possesses a global
SL(2,R) symmetry, which the quantum theory breaks to SL(2,Z). Even if 10-forms have no dynamics, since their field-strength vanishes identically, it is possible to study their behaviour under SL(2,Z) transformations. We determine all the possible independent 10-forms as representations of
SL(2,Z), and in particular we show in which multiplet the RR 10-form lies. Finally, we perform the same analysis for the IIA supersymmetry algebra, and interpret the results in terms of T-duality.
Posted by: KCL
Wed
19 Oct 2005
Quantum communication through spin chains and related systems
Sougato Bose
(University College London)
Abstract:
I will start by introducing a scheme for quantum communication using an unmodulated and unmeasured spin chain. It presents an alternative to converting between static and flying qubits in order to connect up distinct quantum processors. I present some approaches to accomplish perfect quantum communication through a spin chain despite the dispersion of quantum information in the chain. I also discuss the accomplishment of gates between distant spins thorough a spin chain. Apart from transfer, a chain can also be used to simultaneously generate and distribute a maximally entangled state between distant sites, as I illustrate through a chain of coupled qutrits.
I will start by introducing a scheme for quantum communication using an unmodulated and unmeasured spin chain. It presents an alternative to converting between static and flying qubits in order to connect up distinct quantum processors. I present some approaches to accomplish perfect quantum communication through a spin chain despite the dispersion of quantum information in the chain. I also discuss the accomplishment of gates between distant spins thorough a spin chain. Apart from transfer, a chain can also be used to simultaneously generate and distribute a maximally entangled state between distant sites, as I illustrate through a chain of coupled qutrits.
Posted by: CityU
Tue
18 Oct 2005
Supersymmetric Hybrid Inflation and Cosmic Strings
Mairi Sakellariadou
(Kings College, London)
Abstract:
Within supersymmetric grand unified theories, cosmic strings are
generically formed at the end of a hybrid inflationary era.
However, cosmic microwave background measurements imply
severe constraints on the allowed cosmic strings contribution to the
temperature anisotropies.
In the framework of supersymmetry, I will study F- and D-term inflation
and I will set constraints on the free parameters (mass scales and
couplings) of the models, so that there is compatibility between
mixed models (inflation + cosmic strings) and current measurements.
Recently there is a revival in interest for cosmic strings, since ina
ddition,
superstrings could play the role of cosmic strings in theories with large
extra dimensions and moreover it may be that cosmic strings have been
already seen in the sky.
Within supersymmetric grand unified theories, cosmic strings are
generically formed at the end of a hybrid inflationary era.
However, cosmic microwave background measurements imply
severe constraints on the allowed cosmic strings contribution to the
temperature anisotropies.
In the framework of supersymmetry, I will study F- and D-term inflation
and I will set constraints on the free parameters (mass scales and
couplings) of the models, so that there is compatibility between
mixed models (inflation + cosmic strings) and current measurements.
Recently there is a revival in interest for cosmic strings, since ina
ddition,
superstrings could play the role of cosmic strings in theories with large
extra dimensions and moreover it may be that cosmic strings have been
already seen in the sky.
Posted by: IC
Tue
18 Oct 2005
Supersymmetric Hybrid Inflation and Cosmic Strings
Mairi Sakellariadou
(Kings College, London)
Abstract:
Within supersymmetric grand unified theories, cosmic strings are
generically formed at the end of a hybrid inflationary era.
However, cosmic microwave background measurements imply
severe constraints on the allowed cosmic strings contribution to the
temperature anisotropies.
In the framework of supersymmetry, I will study F- and D-term inflation
and I will set constraints on the free parameters (mass scales and
couplings) of the models, so that there is compatibility between
mixed models (inflation + cosmic strings) and current measurements.
Recently there is a revival in interest for cosmic strings, since ina
ddition,
superstrings could play the role of cosmic strings in theories with large
extra dimensions and moreover it may be that cosmic strings have been
already seen in the sky.
Within supersymmetric grand unified theories, cosmic strings are
generically formed at the end of a hybrid inflationary era.
However, cosmic microwave background measurements imply
severe constraints on the allowed cosmic strings contribution to the
temperature anisotropies.
In the framework of supersymmetry, I will study F- and D-term inflation
and I will set constraints on the free parameters (mass scales and
couplings) of the models, so that there is compatibility between
mixed models (inflation + cosmic strings) and current measurements.
Recently there is a revival in interest for cosmic strings, since ina
ddition,
superstrings could play the role of cosmic strings in theories with large
extra dimensions and moreover it may be that cosmic strings have been
already seen in the sky.
Posted by: IC
Mon
17 Oct 2005
Precision Counting of Small Black Holes
Atish Dabholkar
(Tata Institute of Fundamental Research)
Fri
14 Oct 2005
Black Hole Attractors and Entropy
Atish Dabholkar
(Tata Institute of Fundamental Research)
Thu
13 Oct 2005
R4 Corrections to Heterotic M-theory
Lilia Anguelova
(QMW)
Thu
13 Oct 2005
Bethe ansatz in AdS-CFT correspondence
Konstantin Zarembo
(Uppsala / Moscow)
Wed
12 Oct 2005
Matrix models and conformal field theory
📍 London
Ingo Runkel
(KCL)
Abstract:
In this seminar we will look at two places where two-dimensional conformal field theory is related to the study of matrix models. The first is that a matrix model may be thought of as a statistical model on a fluctuating lattice. In the continuum limit, that is in the limit of large matrix size N, this yields a c less than 1 CFT coupled to gravity. The second relation is that the matrix model can, even before the continuum limit, be described in terms of free bosons. The free boson CFT turns out to be useful in understanding the large N behaviour of the matrix model.
In this seminar we will look at two places where two-dimensional conformal field theory is related to the study of matrix models. The first is that a matrix model may be thought of as a statistical model on a fluctuating lattice. In the continuum limit, that is in the limit of large matrix size N, this yields a c less than 1 CFT coupled to gravity. The second relation is that the matrix model can, even before the continuum limit, be described in terms of free bosons. The free boson CFT turns out to be useful in understanding the large N behaviour of the matrix model.
Posted by: KCL
Wed
12 Oct 2005
Living with non-Hermitian Hamiltonians
Hugh Jones
(Imperial College London)
Abstract:
In recent years it has been realized that Hermiticity of the Hamiltonian is not a necessary condition for the reality of its eigenvalues. In many cases it is sufficient for the Hamiltonian to have an unbroken PT symmetry, but the natural Hilbert-space metric of such theories is not positive definite, which raises severe problems as to their physical interpretation. However, it turns out to be possible to construct another,dynamically-determined, metric eta=exp(iQ) that is indeed positive definite. For the most part Q can only be constructed perturbatively,but there are some cases where it is known exactly. With the aid of Q one can construct an equivalent Hermitian Hamiltonian, which, however, may be rather complicated and non-local.
In recent years it has been realized that Hermiticity of the Hamiltonian is not a necessary condition for the reality of its eigenvalues. In many cases it is sufficient for the Hamiltonian to have an unbroken PT symmetry, but the natural Hilbert-space metric of such theories is not positive definite, which raises severe problems as to their physical interpretation. However, it turns out to be possible to construct another,dynamically-determined, metric eta=exp(iQ) that is indeed positive definite. For the most part Q can only be constructed perturbatively,but there are some cases where it is known exactly. With the aid of Q one can construct an equivalent Hermitian Hamiltonian, which, however, may be rather complicated and non-local.
Posted by: CityU
Thu
6 Oct 2005
Twistors, Amplitudes and Unitarity Methods
Emil Bjerrum-Bohr
(Swansea)
Wed
5 Oct 2005
Gauged sigma models and generalised geometry
Jose Figueroa-O'Farrill
(Edinburgh)
Wed
5 Oct 2005
Quantum corrections to spinning strings
Sakura Schafer-Nameki
(Hamburg)
Tue
4 Oct 2005
Knot invariants, q-deformed 2d Yang-Mills and Brownian motion
Sebastian de Haro
(Max Planck Institute)
September 2005
Fri
30 Sep 2005
Topological Mass Generation
Roman Jackiw
(MIT)