Radiation by a heavy quark in N=4 SYM at strong coupling

Using the AdS/CFT correspondence in the supergravity approximation, we compute the energy density radiated by a heavy quark undergoing some arbitrary motion in the vacuum of the strongly coupled N=4 supersymmetric Yang-Mills theory. We find that this energy is fully generated via backreaction from the near-boundary endpoint of the dual string attached to the heavy quark. Because of that, the energy distribution shows the same space-time localization as the classical radiation that would be produced by the heavy quark at weak coupling. We believe that this and some other unnatural features of our result (like its anisotropy and the presence of regions with negative energy density) are artifacts of the supergravity approximation, which will be corrected after including string fluctuations. For the case where the quark trajectory is bounded, we also compute the radiated power, by integrating the energy density over the surface of a sphere at infinity. For sufficiently large times, we find agreement with a previous calculation by Mikhailov [hep-th/0305196].Comment: 22 page

Jet evolution from weak to strong coupling

Recent studies, using the AdS/CFT correspondence, of the radiation produced by a decaying system or by an accelerated charge in the N=4 supersymmetric Yang-Mills theory, led to a striking result: the 'supergravity backreaction', which is supposed to describe the energy density at infinitely strong coupling, yields exactly the same result as at zero coupling, that is, it shows no trace of quantum broadening. We argue that this is not a real property of the radiation at strong coupling, but an artifact of the backreaction calculation, which is unable to faithfully capture the space-time distribution of the radiation. This becomes obvious in the case of a decaying system ('virtual photon'), for which the backreaction is tantamount to computing a three-point function in the conformal gauge theory, which is independent of the coupling since protected by symmetries. Whereas this non-renormalization property is specific to the conformal N=4 SYM theory, we argue that the failure of the three-point function to provide a local measurement is in fact generic: it holds in any field theory with non-trivial interactions. To properly study a localized distribution, one should rather compute a four-point function, as standard in deep inelastic scattering. We substantiate these considerations with studies of the radiation produced by the decay of a time-like photon at both weak and strong coupling. We show that by computing four-point functions, in perturbation theory at weak coupling and, respectively, from Witten diagrams at strong coupling, one can follow the quantum evolution and thus demonstrate the broadening of the energy distribution. This broadening is slow when the coupling is weak but it proceeds as fast as possible in the limit of a strong coupling.Comment: 49 pages, 6 figure

Aspects of the UV/IR correspondence : energy broadening and string fluctuations

We show that a source which radiates in the vacuum of the strongly coupled N=4 SYM theory produces an energy distribution which, in the supergravity approximation, has the same space-time pattern as the corresponding classical distribution: the radiation propagates at the speed of light without broadening. We illustrate this on the basis of several examples: a small perturbation propagating down a steady string, a massless particle falling into AdS_5, and the decay of a time-like wave-packet. A similar observation was made in Phys. Rev. D81 (2010) 126001 for the case of a rotating string. In all these cases, the absence of broadening is related to the fact that the energy backreaction on the boundary arises exclusively from the bulk perturbation at, or near, the boundary. This is so since bulk sources which propagate in AdS_5 at the speed of light do not generate any energy on the boundary. We interpret these features as an artifact of the supergravity approximation, which fails to encode quantum mechanical fluctuations that should be present even in the strong coupling limit. We argue that such fluctuations should enter the dual string theory as longitudinal string fluctuations, which are not suppressed at strong coupling. We heuristically estimate the effects of such fluctuations and argue that they restore the broadening of the radiation, in agreement with expectations from both quantum mechanics and the ultraviolet/infrared correspondence.Comment: 47 page

Pengaruh Pengawasan Komite Audit, Audit Internal, Audit Eksternal Terhadap Kesehatan Keuangan Perusahaan Dan Dampaknya Terhadap Profitabilitas (Studi Pada Perusahaan Asuransi Dan Reasuransi Yang Tercatat Di Bei)

Insurance and reinsurance companies are required, to maintain a sound financial standing and comply with the provisions on the companies equity as stipulated by the government. To achieve such equity, the companies must retain their profitability.  Under a supervision system supported by the audit committee, internal auditor and external auditor, it is expected that the insurance companies shall be able to fulfill their obligation in complying with all the prevailing regulations. If these companies fail to do so, the companies shall be subject to the supervision by the government. This study was conducted on insurance and reinsurance companies listed in the Indonesian Stock Exchange in 2012 (11 companies). Thirty eight high officials of the top management of the companies were interviewed as respondents. By applying the SPSS program the results showed that there are significant relations among the audit committee, the internal and external auditor in supervising the operations of the insurance companies.  There is a positive correlation between the audit committee and the internal auditor; and there is a positive correlation between the audit committee and the external auditor whereas there is also a positive correlation between the internal auditor and the external auditor. Simultaneous influence of the audit committee, the internal audit and the external audit shows a positive effect on the financial soundness. However, external audit has only partial influence on the financial soundness. The simultaneous influence of audit committee, audit internal, audit external and financial soundness shows a significant effect on the profitability. The partial influence on each independent variabel (mentioned above) has a significant effect on the profitability

Analisis Informasi Penentu Harga Saham Saat Initial Public Offering

Salah satu alternatif bagi Perusahaan untuk mendapatkan dana atau modal tambahan adalah dengan melakukan Penawaran Umum Perdana (IPO). Dengan IPO tersebut, Perusahaan harus menyediakan informasi prospektus untuk membantu investor dalam pengambilan keputusan investasi. Fenomena yang sering terjadi pada saat Perusahaan melakukan IPO adalah underpricing pada harga keamanan Perusahaan, di mana investor dapat memperoleh abnormal return, yang tidak mengira akan terjadi sesuai dengan hipotesis pasar yang efisien. Artikel ini bertujuan untuk menguji apakah investor menggunakan atau tidak menggunakan prospektus dalam pengambilan keputusan investasi. Hasil penelitian menunjukkan hanya variabel leverage keuangan yang mempengaruhi return awal ketika Perusahaan melakukan IPO

Deteksi Mutasi Gen Gyrase a Porphyromonas Gingivalis Resisten Terhadap Ciprofloxacin Berdasarkan Teknik Polymerase Chain Reaction

One of resistance mechanisms to ciprofloxacin shown by bacterium Porphyromonas gingivalis isolated from periodontitis patients is mutations of genes through changes in DNA topoisomerase. Ciprofloxacin is an effective antimicrobial for Gram-negative bacteria effectively used for clinical infections treatment. The purpose of this research was to determine the gene mutation of P. gingivalis on periodontitis patients in relation to the resistance to ciprofloxacin by using disc diffusion and, followed by RFLP-PCR on P.gingivalis samples. Based on sensitivity tests by diffusion method, it was shown that the sensitive samples (n =13) had the highest inhibition zone diameter (mean= 25 mm), while the intermediate samples (n=1) was 19 mm. Examination using RFLP-PCR for 14 samples did not reveal any mutation of gyrase A gene

Parton picture for the strongly coupled SYM plasma

Deep inelastic scattering off the strongly coupled N=4 supersymmetric Yang-Mills plasma at finite temperature can be computed within the AdS/CFT correspondence, with results which are suggestive of a parton picture for the plasma. Via successive branchings, essentially all partons cascade down to very small values of the longitudinal momentum fraction x and to transverse momenta smaller than the saturation momentum Q_s\sim T/x. This scale Q_s controls the plasma interactions with a hard probe, in particular, the jet energy loss and its transverse momentum broadening.Comment: 4 pages, Talk given at Quark Matter 2008: 20th International Conference on Ultra-Relativistic Nucleus Nucleus Collisions (QM 2008), Jaipur, India, 4-10 Feb 200