223 research outputs found
Nonstatic AdS_2 Branes and the Isometry Group of AdS_3 Spacetime
For the D-branes on the SL(2,R) WZW model we present a particular choice of
outer automorphism for the gluing condition of currents that leads to a special
AdS_2 brane configuration. This configuration is shown to be a static solution
in the cylindrical coordinates, and a nonstatic solution in the Poincar\'e
coordinates to the nonlinear equation of motion for the Dirac-Born-Infeld
action of a D-string. The generalization of it gives a family of nonstatic
AdS_2 brane solutions. They are deomonstrated to transform to each other under
the isometry group of AdS_3 spacetime.Comment: 11 pages, LaTeX2e, no figure
Physical simulation of wind pressure on building models at various arrangement and airflow conditions
The results of modeling and distribution of the pressure coefficient on the faces of the faces of the model of a high-rise building with a relative height of H/a = 3 and 6 are obtained under the influence of vortex flows created by an obstacle with similar geometric parameters with its lateral displacement from the longitudinal axis of the channel. The accepted range of transverse displacements is L2/a = 0.5; 1; 1.5; 2. In the range of studies, the airflow angle of 0 degrees was adopted with the maximum Reynolds number (Re) = 4.25´104. The distances between the models in the wake correspond to the calibers L1/a = 1.5; 3 and 6. A series of experiments was carried out on the basis of the theory of modeling. The experiments are based on the modeling of the model buildings under study on the basis of the similarity theory. Systematic data are obtained on the distribution of the pressure coefficients Cp on the faces of the model, depending on its location in the track of the upstream model with a change in the distance between them in the transverse direction relative to the direction of the air flow
Spiky strings and single trace operators in gauge theories
We consider single trace operators of the form O_{m_1 ... m_n} = tr D_+^{m_1}
F ... D_+^{m_n} F which are common to all gauge theories. We argue that, when
all m_i are equal and large, they have a dual description as strings with
cusps, or spikes, one for each field F. In the case of N=4 SYM, we compute the
energy as a function of angular momentum by finding the corresponding solutions
in AdS_5 and compare with a 1-loop calculation of the anomalous dimension. As
in the case of two spikes (twist two operators), there is agreement in the
functional form but not in the coupling constant dependence. After that, we
analyze the system in more detail and find an effective classical mechanics
describing the motion of the spikes. In the appropriate limit, it is the same
(up to the coupling constant dependence) as the coherent state description of
linear combinations of the operators O_{m_1 ... m_n} such that all m_i are
equal on average. This agreement provides a map between the operators in the
boundary and the position of the spikes in the bulk. We further suggest that
moving the spikes in other directions should describe operators with
derivatives other than D_+ indicating that these ideas are quite generic and
should help in unraveling the string description of the large-N limit of gauge
theories.Comment: 23 pages, 5 figures. v2: References and comments adde
Dressing the Giant Magnon II
We extend our earlier work by demonstrating how to construct classical string
solutions describing arbitrary superpositions of scattering and bound states of
dyonic giant magnons on S^5 using the dressing method for the SU(4)/Sp(2) coset
model. We present a particular scattering solution which generalizes solutions
found in hep-th/0607009 and hep-th/0607044 to the case of arbitrary magnon
momenta. We compute the classical time delay for the scattering of two dyonic
magnons carrying angular momenta with arbitrary relative orientation on the
S^5.Comment: 13 pages, harvma
Conformal SO(2,4) Transformations for the Helical AdS String Solution
By applying the conformal SO(2,4) transformations to the folded rotating
string configuration with two spins given by a certain limit from the helical
string solution in AdS_3 x S^1, we construct new string solutions whose
energy-spin relations are characterized by the boost parameter. When two
SO(2,4) transformations are performed with two boost parameters suitably
chosen, the straight folded rotating string solution with one spin in AdS_3 is
transformed in the long string limit into the long spiky string solution whose
expression is given from the helical string solution in AdS_3 by making a limit
that the modulus parameter becomes unity.Comment: 16 pages, LaTex, no figure
Neumann and Neumann-Rosochatius integrable systems from membranes on AdS_4xS^7
It is known that large class of classical string solutions in the type IIB
AdS_5xS^5 background is related to the Neumann and Neumann-Rosochatius
integrable systems, including spiky strings and giant magnons. It is also
interesting if these integrable systems can be associated with some membrane
configurations in M-theory. We show here that this is indeed the case by
presenting explicitly several types of membrane embedding in AdS_4xS^7 with the
searched properties.Comment: LaTeX, 17 pages, no figures;v2: comments and citations added;v3: 20
pages, new subsection, explanations, comments and references added; v4: some
typos fixed, to appear in JHE
Giant Magnons under NS-NS and Melvin Fields
The giant magnon is a rotating spiky string configuration which has the same
dispersion relation between the energy and angular momentum as that of a spin
magnon. In this paper we investigate the effects of the NS-NS and Melvin fields
on the giant magnon. We first analyze the energy and angular momenta of the
two-spin spiky D-string moving on the with the NS-NS field.
Due to the infinite boundary of the AdS spacetime the D-string solution will
extend to infinity and it appears the divergences. After adding the counter
terms we obtain the dispersion relation of the corresponding giant magnon. The
result shows that there will appear a prefactor before the angular momentum, in
addition to some corrections in the sine function. We also see that the spiky
profile of a rotating D-string plays an important role in mapping it to a spin
magnon. We next investigate the energy and angular momentum of the one-spin
spiky fundamental string moving on the with the electric or
magnetic Melvin field. The dispersion relation of the corresponding deformed
giant magnon is also obtained. We discuss some properties of the correction
terms and their relations to the spin chain with deformations.Comment: Latex 20 pages, mention D-string and add reference
Sigma model from SU(1,1|2) spin chain
We derive the coherent state representation of the integrable spin chain
Hamiltonian with supersymmetry group . By the use of a projected
Hamiltonian onto bosonic states, we give explicitly the action of the
Hamiltonian on coherent states. Passing to the continuous
limit, we find that the corresponding bosonic sigma model is the sum of the
known SU(2) and SL(2) ones, and thus it gives a string spinning fast on
in . The full sigma model on the supercoset is given.Comment: 20 pages, no figures, 4 tables, 1 appendix; typos corrected,
references adde
Spiky Strings on I-brane
We study rigidly rotating strings in the near horizon geometry of the 1+1
dimensional intersection of two orthogonal stacks of NS5-branes, the so called
I-brane background. We solve the equations of motion of the fundamental string
action in the presence of two form NS-NS fluxes that the I-brane background
supports and write down general form of conserved quantities. We further find
out two limiting cases corresponding to giant magnon and single spike like
strings in various parameter space of solutions.Comment: 17 pages, major restructuring of text, added a referenc
Gauge Theory of the String Geodesic Field
A relativistic string is usually represented by the Nambu-Goto action in
terms of the extremal area of a 2-dimensional timelike submanifold of Minkowski
space. Alternatively, a family of classical solutions of the string equation of
motion can be globally described in terms of the associated geodesic field. In
this paper we propose a new gauge theory for the geodesic field of closed and
open strings. Our approach solves the technical and conceptual problems
affecting previous attempts to describe strings in terms of local field
variables. The connection between the geodesic field, the string current and
the Kalb-Ramond gauge potential is discussed and clarified. A non-abelian
generalization and the generally covariant form of the model are also
discussed.Comment: 38 pages, PHYZZX, UTS-DFT-92-2
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