17778643
Asymptotic Freedom and Dirichlet String Theory
Fixed angle scattering at high energy in a string theory with boundaries satisfying Dirichlet conditions (Dirichlet strings) in D = 4 is shown to have logarithmic dependence on energy, in addition to the power-like behavior known before. High temperature free energy also depends logarithmically on temperature. Such a result could provide a matching mechanism between strings at long distance and asymptotic freedom at short distance, which is necessary for the reformulation of large-N QCD as a string theory. In order to reformulate the large-N QCD [1] as a string theory, assuming it is possible at all, we must find a string theory that contains only massive excitations (for pure QCD) and shares the characteristic features of asymptotic freedom, such as partonic behavior and logarithmic violation of scaling at high energy. The critical string theories we are mostly familiar with fail to meet theses two requirements: they contain massless gravitons and massless Yang-Mill particles, and fixed angle scattering falls off exponentially with total energy. Liouville theory [2] has been argued to be irrelevant for the problem of QCD [3], meanwhile the effective string picture advocated in [4], which without doubt is correct for long strings, has problems at short distances. Rigid strings [5] at first sight seem to give the right behavior at high energy and high temperature, but they have the wrong sign of free energy at high temperature as compared with QCD [6], and furthermore there are problems with unitarity [7]. Another simple yet non-trivial modification of short distance behavior of strings is to add world-sheet boundaries satisfying Dirichlet boundary conditions – each boundary is mapped to a single point in space-time and the position is then integrated over. Such a theory was originally proposed as an off-shell extension of closed string amplitudes [8]. Meanwhile the point-like states of the Dirichlet boundaries were proven to produce powerlike behavior of fixed angle scattering at high energy [9]. The point-like structure was then linked to partons. Developments of the Dirichlet string theory in modern language can be found in [10]. Recently Green [11] points out that at high temperature the Dirichlet boundaries produce a free energy similar to that of the large-N QCD found by Polchinski[6]. Namely, in QCD the free energy of a long string per unit length goes as μQCD(β)/L 2 ∼ − (β)N π2β4 , (1)
14945328
High-temperature partition function of the rigid string.
We find that the high-temperature limit of the free energy per unit length for the rigid string agrees dimensionally with that of the QCD string (unlike the Nambu-Goto string). The sign, and in fact the phase, do not agree. While this may be a clue to a string theory of QCD, we note that the problem of the fourth-derivative action makes it impossible for the rigid string to be a correct description.
8953515
A remark on conformal anomaly and extrinsic geometry of random surfaces
Abstract In low dimensions, conformal anomaly has a profound influence on the critical behavior of random surfaces with extrinsic curvature rigidity 1/ α . We illustrate this by making a small D expansion of rigid random surfaces, where a non-trivial infrared fixed point is shown to exist. We speculate on the renormalization group flow diagram in the (α, D ) plane. We argue that the qualitative behavior of numerical simulations in D =3,4 could be understood on the basis of the phase diagram.
16052098
Three dimensional quantum chromodynamics
The subject of this talk is the study of the low energy behavior of three (2+1) dimensional Quantum Chromodynamics. We show the existence of a phase where parity is unbroken and the flavor group U(2n) is broken into a subgroup U(n)×U(n). We derive the low energy effective action for the theory and show that it has solitonic excitations with Fermi statistic, to be identified with the three dimensional ‘‘baryon’’. Finally, we study the current algebra for this effective action and we find a co‐homologically nontrivial generalization of Kac‐Moody algebras to three dimension.
116802431
Topics in field theory-higher spins, CFT, and gravity
60626146
ILC Reference Design Report: ILC Global Design Effort and World Wide Study
119362042
Deconfinement phase transition in an expanding quark system in the relaxation time approximation
We investigated the effects of nonequilibrium and collision terms on the deconfinement phase transition of an expanding quark system in Friedberg-Lee model in relaxation time approximation. By calculating the effective quark potential, the critical temperature of the phase transition is dominated by the mean field, while the collisions among quarks and mesons change the time structure of the phase transition significantly.
204978414
Evidence for the decay $B_c^+ \rightarrow J/\psi 3\pi^+ 2\pi^-$
Evidence is presented for the decay $B_c+\rightarrow J/\psi 3\pi^+2\pi^-$ using proton-proton collision data, corresponding to an integrated luminosity of 3fb$^{-1}$, collected with the LHCb detector. A signal yield of $32\pm8$ decays is found with a significance of 4.5 standard deviations. The ratio of the branching fraction of the $B_c^+\rightarrow J/\psi 3\pi^+ 2\pi^-$ decay to that of the $B_c^+ \rightarrow J/\psi \pi^+$ decay is measured to be $$ \frac{Br (B_c^+ \rightarrow J/\psi 3\pi^+2\pi^)}{Br (B_c^+ \rightarrow J/\psi \pi^+)} = 1.74\pm0.44\pm0.24, $$ where the first uncertainty is statistical and the second is systematic.
94329078
Chiral Phase Transition Around the Tricritical Point
118413429
Simulation Study on neutrino nucleus cross section measurement in Segmented Detector at Spallation Neutron Source
Knowledge of νe-Fe/Pb differential cross sections for νe energy below several tens of MeV scale is believed to be crucial in understanding Supernova physics. In a segmented detector at Spallation Neutrino Source, νe energy reconstructed from the electron range measurement is strongly affected because of both multiple scattering and electromagnetic showers occurring along the electron passage in target materials. In order to estimate the effect, a simulation study has been performed with a cube block model assuming a perfect tracking precision. The distortion of energy spectrum is observed to be proportional to the atomic number of target material. Feasibility of unfolding the distorted νe energy spectrum is studied for both Fe and Pb cases. Evaluation of statistical accuracy attainable is therefore provided for a segmented detector.