119104739
Noncommutative M-branes from Covariant Open Supermembranes
We discuss an open supermembrane in the presence of a constant three-form. The boundary conditions to ensure the �-invariance of the action lead to possible Dirichlet branes. It is shown that a noncommutative (NC) M5-brane is possible as a boundary and the self-duality condition that the flux on the world-volume satisfies is derived from the requirement of the �-symmetry. We also find that the open supermembrane can attach to each of infinitely many M2-branes on an M5-brane, namely a strong flux limit of the NC M5-brane. PACS numbers: 11.25.Yb, 11.25.Uv, 11.25.-w, 11.25.Wx Open supermembranes [1] are attractive objects. Supermembranes [2] are considered as fundamental objects of M-theory [3], which is believed to be the unified theory of superstrings, and open supermembranes are especially interesting because of connection to some realistic phenomenological models via the Horava-Witten scenario [4]. It is well-known that an open supermembrane in flat spacetime can attach on Dirichlet p-branes with p = 1,5 and 9 [5, 6]. The p = 5 case corresponds to M5-brane and the case with p = 9 is nothing but the end of the world nine-brane discussed in the Horava-Witten theory [4]. As a recent progress, open M5-branes have also been discussed in [7]. It is interesting to consider a generalization of studies of open supermembranes by including constant threeform gauge field (gauge field condensate). In this direction an approach based on the light-cone gauge, with which supermembrane theory is well studied, is not desirable because the light-cone coordinates should inevitably be Neumann directions and furthermore one cannot consider arbitrary electric fluxes. Thus a covariant approach is more appropriate for our purpose [8]. In this letter we basically follow the covariant procedure utilized in [5]. This type of procedure was used to study D-branes of Green-Schwarz (GS) string theories in [9]. We discuss NC M5-branes from the requirement of the κ-symmetry of a covariant GS action of an open supermembrane with constant fluxes. In case of open supermembrane, the surface terms appear under the κ-variation of the action and hence they should be deleted by imposing some appropriate boundary conditions. The usual NC M5-branes are surely included among the conditions, for which the self-duality condition of the flux on the worldvolume is also obtained from the condition that the projection operator should satisfy. In addition, p = 2 case is
18362159
Partition function and open/closed string duality in type IIA string theory on a pp-wave
Abstract We discuss partition functions of N =(4,4) type IIA string theory on the pp-wave background. This theory is shown to be modular invariant. The boundary states are constructed and possible D-brane instantons are classified. Then we calculate cylinder amplitudes in both closed and open string descriptions and check the open/closed string duality. Furthermore we consider general properties of modular invariant partition functions in the case of pp-waves.
119327427
Hidden Yangian symmetry in sigma model on squashed sphere
We discuss a hidden symmetry of a two-dimensional sigma model on a squashed S3. The SU(2) current can be improved so that it can be regarded as a flat connection. Then we can obtain an infinite number of conserved non-local charges and show the Yangian algebra by directly checking the Serre relations. This symmetry is also deduced from the coset structure of the squashed sphere. The same argument is applicable to the warped AdS3 spaces by the double Wick rotations.
2088281
A tunneling picture of dual giant Wilson loop
We further discuss a rotating dual giant Wilson loop (D3-brane) solution constructed in Lorentzian AdS by Drukker et al. The solution is shown to be composed of a dual giant Wilson loop and a dual giant graviton by minutely examining its shape. Hence it may be supposed that the dual gauge-theory operator should be a k-th symmetric Wilson loop with insertions of dual giant graviton operators. To give a convincing argument for this observation, the classical action of the solution should be evaluated in Euclidean signature. For this purpose we perform a Wick rotation to the Lorentzian solution by following the tunneling prescription and obtain Euclidean solutions attaching to a circle or a straight line on the AdS boundary. The classical action contains a logarithmic divergence which is proportional to the R-charge. It is consistent with the correlation function of the dual giant graviton operators. Because of ambiguities concerning regularization, finite terms of the action do not lead to conclusive evidence. However we may expect that the ambiguities would cancel by subtracting the action of the D3-brane with a straight-line boundary from that with a circular boundary. It is really shown that the difference is consistent with the expectation value of the k-th symmetric Wilson loop. Although our analysis does not specify the unique dual gauge-theory operator, we discuss possible candidates implied by the D3-brane computation.
15711173
Non-relativistic string and D-branes on AdS5 × S5 from semiclassical approximation
We show that non-relativistic actions of string and D-branes on AdS5???S5 can be reproduced as a semiclassical approximation of the string and D-brane actions around static 1/2 BPS configurations. This is contrastive to the Penrose limit. For example, the pp-wave string can be recaptured as a semiclassical approximation around a 1/2 BPS particle rotating at the velocity of light. We argue that small deformation of a straight Wilson line would give a composite operator in the gauge-theory side that corresponds to a semiclassical state of the non-relativistic string, according to the semiclassical interpretation.
119324390
Hybrid classical integrable structure of squashed sigma models - a short summary
We give a short summary of our recent works on the classical integrable structure of two-dimensional non-linear sigma models defined on squashed three-dimensional spheres. There are two descriptions to describe the classical dynamics, 1) the rational description and 2) the trigonometric description. It is possible to construct two different types of Lax pairs depending on the descriptions, and the classical integrability is shown by computing classical r/s-matrices satisfying the extended Yang-Baxter equation in both descriptions. In the former the system is described as an integrable system of rational type. On the other hand, in the latter it is described as trigonometric type. There exists a non-local map between the two descriptions and those are equivalent. This is a non-local generalization of the left-right duality in principal chiral models.
120128880
Negative pion production in subthreshold heavy ion collisions
Abstract Inclusive π− spectra have been measured for 14N+C collisions at 41A, 67A, 80A and 135A MeV, the lowest energies measured for the charged pion. The cross sections fall exponentially with Tπ and the exponential slope factors at 90° in the nucleon-nucleon center of mass frame are determined. Energy distributions below a beam energy of 100A MeV are less steep than expected from the monotonic decrease of the slope factor down to 100A MeV. The production mechanism of energetic pions far below threshold is discussed for several models.
120103770
Determination of the density distribution and the correlation of halo neutrons in 11Li
Interaction cross sections (σ1) and transverse momentum Pt distributions of 9Li fragments in 11Li reactions were measured 1467 using p and d targets at 800A MeV, and Be and C targets at 400A MeV. The density distribution of the 11Li nucleus has been determined for the first time from these σI's. It is confirmed that only a distribution with a long tail (halo) consistently reproduces the observed data. From a combined analysis of Pt distributions of 9Li and of neutrons, the momentum correlation of the two halo neutrons was extracted. It suggests that these neutrons have a strong tendency to move in the same direction.
15470225
Analysis of the phase structure of thermal QED/QCD through the HTL improved ladder Dyson-Schwinger equation: On the gauge dependence of the solution
We solved with a numerical procedure the HTL improved ladder DS equation for the retarded fermion self-energy function $\Sigma_R$ to study the spontaneous generation of fermion mass in thermal QCD/QED, and studied the gauge-dependence of the solution within a general covariant gauge where the gauge parameter $\xi$ is any constant number. 
With the numerical solutions thus obtained, we found the followings; i) The fermion wave function renormalization function $A(P)$ always deviates largely from unity even at the momentum where the mass is defined, thus the corresponding solutions explicitly contradict with the Ward-Takahashi identity. ii) As a result, the obtained solutions strongly depend on the choice of gauge parameters: the critical temperatures and the critical coupling constants significantly change gauge by gauge. In all gauges we studied in the present analysis, we could not find any solution, having a possibility to be consistent with the Ward-Takahashi identity. Thus we are forced to investigate the procedure to find a gauge which enables us to get a solution being consistent with the Ward-Takahashi identity, otherwise we can not obtain any physically sensible conclusions through the analysis of the point-vertex ladder DS equation no matter how the gauge propagator gets improved.
119480216
Chiral Phase Transitions in QED at Finite Temperature Dyson-Schwinger Equation Analysis in the Real Time Hard-Thermal-Loop Approximation
In order to clarify the essential thermal effects that govern the chiral phase transition at finite temperature, we investigate, in the real-time thermal QED, the consequences of the hard-thermal-loop (HTL) resummed Dyson-Schwinger equation for the physical fermion mass function ΣR. Since ΣR is the mass function of an “unstable” quasi-particle in thermal field theories, it necessarily has non-trivial imaginary parts, together with non-trivial wave function renormalization constants. Analyses so far have completely disregarded this fact, despite it being one of the basic outcomes of thermal field theory. The “approximation”, which ignores the imaginary parts of ΣR, gives (non-trivial) constraint equations to be solved simultaneously. For this reason, this approximation cannot be applied consistently except in the trivial case, ΣR = 0. In the present analysis we correctly take this fact into account, and study, in the ladder approximation, the effect of the HTL resummed gauge boson propagator. Our results obtained using numerical analysis, reveal two facts: i) the chiral phase transition is of second order, since the fermion mass is dynamically generated at a critical value of the temperature Tc, or at a critical coupling constant αc, without any discontinuity; and ii) the critical temperature Tc at a fixed value of α is significantly lower than that obtained previously, which means that the restoration of chiral symmetry occurs at a lower temperature than previously expected. The second fact shows the importance of correctly incorporating the essential thermal effect into the analysis of the chiral phase transition. A procedure for taking account of the gauge invariance in the present approximation is also discussed.
102941799
Experimental study of neutron rich helium isotopes