Remark on the open string pair production enhancement

Recent studies by one of the present authors along with his collaborators in [1-4] show that there exist the so-called open string pair production for a possible simplest system of two Dp branes, placed parallel at a separation and with each carrying different electric flux, in Type II superstring theories. Further this pair production can be greatly enhanced when a magnetic flux, sharing no common field strength index with the electric one, is added, implying then $p \ge 3$. Given this, one may wonder if further enhancement can be achieved by adding more magnetic flux(es) in a similar fashion. In this paper, we explore this possibility. It turns out that adding more such magnetic flux diminishes rather than enhances the pair production rate. This actually implies that the largest enhancement occurs at $p = 3$ when the same realistic electric and magnetic fluxes are applied for all $p \ge 3$. Curiously one of D3 branes may be our own world and if so, the enhancement gives a possible opportunity to detect the pair production, therefore to test the underlying string theories.Comment: 14 pages, 0 figure

On 1/4 BPS ((F, D1), (NS5, D5)) bound states of type IIB string theory

We construct two new SL(2,Z) invariant vacua of type IIB string theory which are bound states of $(p,q)$ strings with $(m,n)$ 5-branes, written as ((F, D1), (NS5, D5)) and preserve 1/4 of the full space-time supersymmetries. For the first case, the strings live inside the 5-brane world-volume and in the second case the strings are perpendicular to the 5-brane world-volume. In the first case, naively one would expect an attractive interaction between the strings and the 5-branes due to attractive force between F and D5 and also between D1 and NS5. We find that 1/4 BPS bound state exists only when the vacuum moduli satisfy certain condition which is found to be consistent with the no-force condition between the branes. No such complication arises for the second case. The tension formulae and the various other descendant states which can be obtained by the application of T-duality for both these bound states are discussed.Comment: 22 pages, 1 table, minor changes and one reference added, the version to appear in JHE

Memory-Efficient Topic Modeling

As one of the simplest probabilistic topic modeling techniques, latent Dirichlet allocation (LDA) has found many important applications in text mining, computer vision and computational biology. Recent training algorithms for LDA can be interpreted within a unified message passing framework. However, message passing requires storing previous messages with a large amount of memory space, increasing linearly with the number of documents or the number of topics. Therefore, the high memory usage is often a major problem for topic modeling of massive corpora containing a large number of topics. To reduce the space complexity, we propose a novel algorithm without storing previous messages for training LDA: tiny belief propagation (TBP). The basic idea of TBP relates the message passing algorithms with the non-negative matrix factorization (NMF) algorithms, which absorb the message updating into the message passing process, and thus avoid storing previous messages. Experimental results on four large data sets confirm that TBP performs comparably well or even better than current state-of-the-art training algorithms for LDA but with a much less memory consumption. TBP can do topic modeling when massive corpora cannot fit in the computer memory, for example, extracting thematic topics from 7 GB PUBMED corpora on a common desktop computer with 2GB memory.Comment: 20 pages, 7 figure

Delayed hepatic rupture post ultrasound-guided percutaneous liver biopsy: A case report.

RATIONALE: Hemorrhage, one of complications after liver biopsy, is often identified immediately after the procedure while delayed liver rupture is relatively rare. PATIENT CONCERNS: A 45-year-old woman was diagnosed with undetermined liver cirrhosis and abnormal liver function. To determine the etiology and severity of liver cirrhosis, ultrasound-guided liver biopsy was arranged. The patients did not complain any pain during the procedure. Ultrasound examination on postoperative day1 (POD 1) and MRI on POD 3 showed no evidence of hematoma and ascites. On POD 7, however, the patient was taken to the hospital with a sudden onset of pain in the right upper quadrant of the abdomen. DIAGNOSES: Contrast-enhanced computed tomography revealed liver rupture of right inferior segment of the liver with subcapsular hematoma. INTERVENTIONS: Patient was treated with infusion of 2-unit red blood cell suspension, fluid and hemostatics. OUTCOMES: The vital signs of the patient were stabilized after the therapy. The follow-up ultrasound 1 month later showed a shrunken subcapsular hematoma measuring 4.2 × 2.1 cm at the right lobe. LESSONS: Whenever a liver biopsy procedure is performed, the care should be taken to avoid puncturing those areas that may have liver incisure. Moreover, the patient need to rest for several days and to avoid heavy activities, which is one of the major risk factors for post-procedure bleeding

Matter Power Spectra in Viable f(R)f(R) Gravity Models with Massive Neutrinos

We investigate the matter power spectra in the power law and exponential types of viable $f(R)$ theories along with massive neutrinos. The enhancement of the matter power spectrum is found to be a generic feature in these models. In particular, we show that in the former type, such as the Starobinsky model, the spectrum is magnified much larger than the latter one, such as the exponential model. A greater scale of the total neutrino mass, $\Sigma m_{\nu}$, is allowed in the viable $f(R)$ models than that in the $\Lambda$CDM one. We obtain the constraints on the neutrino masses by using the CosmoMC package with the modified MGCAMB. Explicitly, we get $\Sigma m_{\nu} < 0.451 \ (0.214)\ \mathrm{eV}$at 95the corresponding one for the$\Lambda$CDM model is$\Sigma m_{\nu} < 0.200\ \mathrm{eV}$. Furthermore, by treating the effective number of neutrino species$N_{\mathrm{eff}}$as a free parameter along with$\Sigma m_{\nu}$, we find that$N_{\mathrm{eff}} = 3.78^{+0.64}_{-0.84} (3.47^{+0.74}_{-0.60})$and$\Sigma m_{\nu} = 0.533^{+0.254}_{-0.411}$($< 0.386) \ \mathrm{eV}$ at 95% C.L. in the Starobinsky (exponential) model.Comment: 15 pages, 5 figures, updated version accepted by PL