209 research outputs found
On string integrability. A journey through the two-dimensional hidden symmetries in the AdS/CFT dualities
One of the main topics in the modern String Theory are the AdS/CFT dualities.
Proving such conjectures is extremely difficult since the gauge and string
theory perturbative regimes do not overlap. In this perspective, the discovery
of infinitely many conserved charges, i.e. the integrability, in the planar
AdS/CFT has allowed us to reach immense progresses in understanding and
confirming the duality. We review the fundamental concepts and properties of
integrability in two-dimensional sigma-models and in the AdS/CFT context. The
first part is focused on the AdS_5/CFT_4 duality, especially the classical and
quantum integrability of the type IIB superstring on AdS_5 x S^5 are discussed
in both pure spinor and Green-Schwarz formulations. The second part is
dedicated to the AdS_4/CFT_3 duality with particular attention to the type IIA
superstring on AdS_4 x CP^3 and its integrability. This review is based on a
shortened and revised version of the author's PhD thesis, discussed at Uppsala
University in September 2009.Comment: 116 pages, 11 figures, to be published in Advances in High Energy
Physics, Special Issue on ''Gauge/String Duality'
Aspects of quantum integrability for pure spinor superstring in AdS(5)xS(5)
We consider the monodromy matrix for the pure spinor IIB superstring on
at leading order at strong coupling, in particular its
variation under an infinitesimal and continuous deformation of the contour.
Such variation is equivalent to the insertion of a local operator. Demanding
the BRST-closure for such an operator rules out its existence, implying that
the monodromy matrix remains contour-independent at the first order in
perturbation theory. Furthermore we explicitly compute the field strength
corresponding to the flat connections up to leading order and directly check
that it is free from logarithmic divergences. The absence of anomaly in the
coordinate transformation of the monodromy matrix and the UV-finiteness of the
curvature tensor finally imply the integrability of the pure spinor superstring
at the first order.Comment: 44 pages; 4 figure
Glycolaldehyde, methyl formate and acetic acid adsorption and thermal desorption from interstellar ices
We have undertaken a detailed investigation of the adsorption, desorption and thermal processing of the astrobiologically significant isomers glycolaldehyde, acetic acid and methyl formate. Here, we present the results of laboratory infrared and temperature programmed desorption (TPD) studies of the three isomers from model interstellar ices adsorbed on a carbonaceous dust grain analogue surface. Laboratory infrared data show that the isomers can be clearly distinguished on the basis of their infrared spectra, which has implications for observations of interstellar ice spectra. Laboratory TPD data also show that the three isomers can be distinguished on the basis of their thermal desorption behaviour. In particular, TPD data show that the isomers cannot be treated the same way in astrophysical models of desorption. The desorption of glycolaldehyde and acetic acid from water-dominated ices is very similar, with desorption being mainly dictated by water ice. However, methyl formate also desorbs from the surface of the ice, as a pure desorption feature, and therefore desorbs at a lower temperature than the other two isomers. This is more clearly indicated by models of the desorption on astrophysical time-scales corresponding to the heating rate of 25 and 5 Mâ stars. For a 25 Mâ star, our model shows that a proportion of the methyl formate can be found in the gas phase at earlier times compared to glycolaldehyde and acetic acid. This has implications for the observation and detection of these molecules, and potentially explains why methyl formate has been observed in a wider range of astrophysical environments than the other two isomers
Trapping and desorption of complex organic molecules in water at 20 K
The formation, chemical and thermal processing of complex organic molecules (COMs) is currently a topic of much interest in interstellar chemistry. The isomers glycolaldehyde, methyl formate and acetic acid are particularly important because of their role as pre-biotic species. It is becoming increasingly clear that many COMs are formed within interstellar ices which are dominated by water. Hence the interaction of these species with water ice is crucially important in dictating their behaviour. Here we present the first detailed comparative study of the adsorption and thermal processing of glycolaldehyde, methyl formate and acetic acid adsorbed on and in water ices at astrophysically relevant temperatures (20 K). We show that the functional group of the isomer dictates the strength of interaction with water ice, and hence the resulting desorption and trapping behaviour. Furthermore, the strength of this interaction directly affects the crystallization of water, which in turn affects the desorption behaviour. Our detailed coverage and composition dependent data allow us to categorize the desorption behaviour of the three isomers on the basis of the strength of intermolecular and intramolecular interactions, as well as the natural sublimation temperature of the molecule. This categorization is extended to other C, H and O containing molecules in order to predict and describe the desorption behaviour of COMs from interstellar ices
Operator Product Expansion for Pure Spinor Superstring on AdS(5)*S(5)
The tree-level operator product expansion coefficients of the matter currents
are calculated in the pure spinor formalism for type IIB superstring in the
AdS(5)*S(5) background.Comment: 18 pages, no figure, corrected typos and added acknowledgement
Quantized Strings and Instantons in Holography
We study worldsheet instantons in holographic type IIA backgrounds directly
in string theory. The first background is a dimensional reduction of
AdS and is dual to the maximally supersymmetric Yang-Mills theory
on . The second background is AdS dual to ABJM in
the type IIA limit. We compute the one-loop partition function of the
fundamental string in these backgrounds and show that the result is in exact
agreement with field theory predictions. We argue that for higher rank
instantons, the string partition function takes a product form of the single
instanton partition function times the contribution of two orbifolds on the
worldsheet. We determine the orbifold factor to be where is the
instanton rank. With this result, we reproduce the series of non-perturbative
corrections in to the planar free energy. When studying the
worldsheet instanton partition function on , we encounter twelve
fermionic and twelve bosonic zero modes. By deforming the ABJM theory, the
zero-modes are lifted and consequently the tower of worldsheet instantons can
be evaluated and matched to known results in the QFT. As a by-product, we
determine a series of higher rank instanton corrections to the free energy of
the mass-deformed and orbifolded ABJ(M) theory.Comment: 35 pages. v2: Minor correction
Finite-size corrections in the SU(2) x SU(2) sector of type IIA string theory on AdS_4 x CP^3
We consider finite-size corrections in the SU(2) x SU(2) sector of type IIA
string theory on AdS_4 x CP^3, which is the string dual of the recently
constructed N=6 superconformal Chern-Simons theory of Aharony, Bergman,
Jafferis and Maldacena (ABJM theory). The string states we consider are in the
R x S^2 x S^2 subspace of AdS_4 x CP^3 with an angular momentum J on CP^3 being
large. We compute the finite-size corrections using two different methods, one
is to consider curvature corrections to the Penrose limit giving an expansion
in 1/J, the other by considering a low energy expansion in lambda'=lambda/J^2
of the string theory sigma-model, lambda being the 't Hooft coupling of the
dual ABJM theory. For both methods there are interesting issues to deal with.
In the near-pp-wave method there is a 1/\sqrt{J} interaction term for which we
use zeta-function regularization in order to compute the 1/J correction to the
energy. For the low energy sigma-model expansion we have to take into account a
non-trivial coupling to a non-dynamical transverse direction. We find agreement
between the two methods. At order lambda' and lambda'^2, for small lambda', our
results are analogous to the ones for the SU(2) sector in type IIB string
theory on AdS_5 x S^5. Instead at order lambda'^3 there are interactions
between the two two-spheres. We compare our results with the recently proposed
all-loop Bethe ansatz of Gromov and Vieira and find agreement.Comment: 21 pages. v2: typos fixed, refs. added. v3: misprints corrected,
refs. adde
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Remarks on the geometrical properties of semiclassically quantized strings
We discuss some geometrical aspects of the semiclassical quantization of string solutions in type IIB GreenâSchwarz action on ADS5xS5 We concentrate on quadratic fluctuations around classical configurations, expressing the relevant differential operators in terms of (intrinsic and extrinsic) invariants of the background geometry. The aim of our exercise is to present some compact expressions encoding the spectral properties of bosonic and fermionic fluctuations. The appearing of non-trivial structures on the relevant bundles and their role in concrete computations are also considered. We corroborate the presentation of general formulas by working out explicitly a couple of relevant examples, namely the spinning string and the latitude BPS Wilson loop
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