arXiv subjects

Sourav Maji

Publications and source records attributed to Sourav Maji.

10 recordsLinked to original sources

arXiv2026

Tropical Open Strings in a Kalb-Ramond Background

We study tropical open strings arising from the analytically continued action of tropological sigma models in the presence of a constant Kalb-Ramond background. We show that the background field separates the theory into a generic sector and a critical sector. In the generic sector, the canonical structure produces a kinematical nonlocal bracket between the transverse and leafwise target-space coordinates. At the critical value of the Kalb-Ramond field, the Legendre map degenerates and the theory develops a primary constraint, requiring quantization by the Dirac-Bergmann procedure. This critical sector has a finite reduced phase-space structure and differs from the naive limit of the generic theory.

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arXiv2026

BRST quantization of Carroll-Weyl gauged null strings

We study the BRST quantization of the null string after completing its local gauge symmetry by Carroll-Weyl transformations. The resulting worldsheet theory possesses three first-class constraints, $C_1 = P^2$, $C_2 = P \cdot X'$, and $C_3 = P \cdot X$, whose modes realize a Weyl-BMS algebra. The additional Carroll-Weyl constraint qualitatively changes the quantum gauge complex: its scalar $s$-ghost is intrinsically coupled to the BMS $bc$-ghost sector, and the anomaly analysis involves three independent cocycles rather than a single Virasoro-type central charge. Starting from the gauge-fixed action, we derive the complete Faddeev-Popov complex, construct the matter and ghost currents and the BRST charge, and evaluate their equal-time operator products in the flipped, equivalently highest-weight, representation. The matter and ghost anomaly coefficients are $(c_{LL},c_{LS},c_{SS})_{\mathrm{matter}}=(2D,-D,-D)$ and $(c_{LL},c_{LS},c_{SS})_{\mathrm{ghost}}=(-54,6,4)$. Because the corresponding central terms multiply linearly independent ghost bilinears in $Q_B^2$, BRST nilpotency requires the three conditions $D=27$, $D=6$, and $D=4$, respectively. These conditions are mutually incompatible. Consequently, there is no target-space dimension in which the minimal flat Carroll-Weyl matter-plus-ghost complex is anomaly-free in the highest-weight representation. The familiar $D=26$ condition of the ILST null string is recovered only after truncation to the two-constraint BMS subsector, which defines a different quantum gauge complex.

hep-th↗

arXiv2026

Path integral quantization of null bosonic strings with Carroll-Weyl ghosts

We revisit the path integral quantization of the null bosonic string from the viewpoint that all local gauge symmetries of the Carrollian worldsheet must be gauge fixed before the quantum theory is defined. In the tensile-string construction the $bc$ ghosts are the Faddeev-Popov determinant for fixing $\mathrm{Diff}\times\mathrm{Weyl}$. In the ILST null string this logic gives the BMS $bc$ system. However, a Carrollian worldsheet admits an additional volume-preserving Carroll-Weyl scaling, whose Hamiltonian generator is $C_3=P\cdot X$. Keeping this scaling as a genuine local gauge symmetry adds one more Faddeev-Popov row. The correct ghost system is therefore a $bcs$ system: the BMS $bc$ ghosts plus a scalar ghost $s$ and scalar antighost $b^s$ for Carroll-Weyl scaling. We derive the revised path integral, the $bcs$-ghost action, its residual symmetry equations, mode expansion, and its relation to the extended BMS algebra. The result changes the BRST complex and the anomaly problem: the usual $D=26$ check based only on the old BMS $bc$ ghosts is a partially gauge-fixed calculation, while the Carroll-Weyl covariant quantum theory must include the $s,b^s$ sector.

hep-th↗

arXiv2026

From closed to open strings: the tensionless route in Kalb-Ramond background and noncommutativity

We study tensionless bosonic strings propagating in the presence of a constant Kalb--Ramond background and show how closed strings undergo a transition into open strings. Working in the intrinsically tensionless theory, we show that the Carrollian limit of the closed-string worldsheet induces a universal gluing of `left'- and `right'-moving oscillators, which is deformed in the presence of the background $B$-field. From the action we derive the mixed boundary conditions, construct the corresponding gluing matrix, and obtain the induced vacuum as a squeezed boundary state. This gives a first-principles realization of the closed-to-open string transition in the tensionless regime. We further extend the analysis to toroidal compactification and show that the worldsheet Bose--Einstein-like condensation mechanism continues to hold in the presence of the $B$-field. Second, we analyze boundary noncommutativity in a unified symplectic framework, both in the tensile theory and in the tensionless regime. In the tensile strings, we show that the boundary symplectic form reproduces the Seiberg--Witten noncommutative parameter. We then study the tensionless limit of this construction and show that the boundary $B$-field term remains as the unique surviving source of the symplectic structure. We derive the same structure directly in the intrinsically tensionless strings, where the inverse boundary symplectic form defines the noncommutative parameter of the null string.

hep-th↗

arXiv2026

Covariant phase space approach to noncommutativity in tensile and tensionless open strings

We study noncommutativity in open strings using the covariant phase space formalism. For tensile open strings in a constant Kalb-Ramond background, we show that the (pre)-symplectic current splits into a bulk kinetic term plus an exact boundary term, recovering the Seiberg-Witten noncommutativity parameter. We then extend the analysis to intrinsically tensionless strings. In the absence of background fields, the reduced phase space is degenerate and carries no intrinsic Poisson structure. In the presence of a constant Kalb-Ramond field, the symplectic current localises entirely on the boundary, so that the physical phase space becomes purely boundary-supported and the endpoint coordinates acquire a noncommutative Poisson algebra. Including a boundary gauge-field coupling similarly leads to a boundary symplectic form governed by the effective Born-Infeld combination on the D-brane. Our results provide a unified description of noncommutativity in both tensile and tensionless open strings.

hep-th↗

arXiv2026

Pure D-brane Black Holes: BPS Counting and non-BPS Vacua

In this paper, we present a unified computational framework to analyze the microscopic vacuum structure of 4-charge extremal black holes in Type IIA string theory, applying techniques from computational algebraic geometry and numerical topology to their pure D-brane effective quantum mechanics. We apply this approach to two physically distinct configurations. First, in the supersymmetric sector, we compute the $14^{\text{th}}$ helicity trace index of $\frac{1}{8}$-BPS, $N=8$, D2-D2-D2-D6 configurations dual to D1-D5-P-KK monopole dyonic black holes. Extending previous work to higher charges, we employ a parametric monodromy method to explicitly resolve the vacua for the $(1,1,1,5)$ and $(1,1,1,6)$ configurations, reproducing the degeneracies predicted by the U-dual picture. Second, we apply complementary techniques to a configuration where supersymmetry is explicitly broken at the level of the effective action. The corresponding 4-charge non-BPS extremal pure D-brane system is obtained by replacing the D6-brane with an anti-D6-brane and assigning incompatible R-symmetry rotations to different brane triplets. Analyzing the associated scalar potential using analytical Gr\"obner bases, we demonstrate the absence of zero-energy classical ground states. To handle the continuous flat directions populating the non-BPS landscape, we implement specific topological regularizations, namely Morse-Bott deformations and gated soft-trapping. These methods allow us to systematically characterize the classical energy landscape, identifying a non-compact Coulomb branch, marginally bound stabilizer submanifolds, and an isolated collection of doubly degenerate low-energy stable states.

hep-th↗

arXiv2025

Information Scrambling with Higher-Form Fields

The late time behaviour of OTOCs involving generic non-conserved local operators show exponential decay in chaotic many body systems. However, it has been recently observed that for certain holographic theories, the OTOC involving the $U(1)$ conserved current for a gauge field instead varies diffusively at late times. The present work generalizes this observation to conserved currents corresponding to higher-form symmetries that belong to a wider class of symmetries known as generalized symmetries. We started by computing the late time behaviour of OTOCs involving $U(1)$ current operators in five dimensional AdS-Schwarzschild black hole geometry for the 2-form antisymmetric $B$-fields. The bulk solution for the $B$-field exhibits logarithmic divergences near the asymptotic AdS boundary which can be regularized by introducing a double trace deformation in the boundary CFT. Finally, we consider the more general case with antisymmetric $p$-form fields in arbitrary dimensions. In the scattering approach, the boundary OTOC can be written as an inner product between asymptotic 'in' and 'out' states which in our case is equivalent to computing the inner product between two bulk fields with and without a shockwave background. We observe that the late time OTOCs have power law tails which seems to be a universal feature of the higher-form fields with $U(1)$ charge conservation.

hep-th↗

arXiv2024

Spectral representation in Klein space: simplifying celestial leaf amplitudes

In this paper, we explore the spectral representation in Klein space, which is the split $(2,2)$ signature flat spacetime. The Klein space can be foliated into Lorentzian $\mathrm{AdS}_3 /\mathbb{Z}$ slices, and its identity resolution has continuous and discrete parts. We calculate the identity resolution and the Plancherel measure in these slices. Using the foliation of Klein space into the slices, the identity resolution, and the Plancherel measure in each slice, we compute the spectral representation of the massive bulk-to-bulk propagator in Klein space. It can be expressed as the sum of the product of two massive (or tachyonic) conformal primary wavefunctions, with both continuous and discrete parts, and sharing a common boundary coordinate. An interesting point in Klein space is that, since the identity resolution has discrete and continuous parts, a new type of conformal primary wavefunction naturally arises for the massive (or tachyonic) case. For the conformal primary wavefunctions, both the discrete and continuous parts involve integrating over the common boundary coordinate and the real (or imaginary) mass. The conformal dimension is summed in the discrete part, whereas it is integrated in the continuous part. The spectral representation in Klein space is a computational tool to derive conformal block expansions for celestial amplitudes in Klein space and its building blocks, called celestial leaf amplitudes, by integrating the particle interaction vertex over a single slice of foliation.

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arXiv2024

Counting $\mathcal{N} = 8$ Black Holes as Algebraic Varieties

We calculate the helicity trace index $B_{14}$ for $\mathcal{N} = 8$ pure D-brane black holes using various techniques of computational algebraic geometry and find perfect agreement with the existing results in the literature. For these black holes, microstate counting is equivalent to finding the number of supersymmetric vacua of a multi-variable supersymmetric quantum mechanics which in turn is equivalent to solving a set of multi-variable polynomial equations with syzygies. We explore four different techniques to solve a set of polynomial equations, namely Newton Polytopes, Homotopy continuation, Monodromy and Hilbert series. Unlike other schemes, these methods are almost exact with a very high success rate for finding all solutions. A gauge invariant analysis is also possible using the symbolic Hilbert series. Furthermore, exploiting various exchange symmetries, we show the non-existence of a quartic and(or) higher order terms in the potential which if present would have spoiled the counting. Incorporating recent developments in mathematics, algorithms and multi-threading, we have extended the scope of one of the author's previous works to other charges and presented a new perspective for the microstate counting problem. This further establishes the pure D-brane system as a consistent model, bringing us a step closer to $\mathcal{N} = 2$ black hole counting.

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arXiv2018

High Speed Elephant Flow Detection Under Partial Information

In this paper we introduce a new framework to detect elephant flows at very high speed rates and under uncertainty. The framework provides exact mathematical formulas to compute the detection likelihood and introduces a new flow reconstruction lemma under partial information. These theoretical results lead to the design of BubbleCache, a new elephant flow detection algorithm designed to operate near the optimal tradeoff between computational scalability and accuracy by dynamically tracking the traffic's natural cutoff sampling rate. We demonstrate on a real world 100 Gbps network that the BubbleCache algorithm helps reduce the computational cost by a factor of 1000 and the memory requirements by a factor of 100 while detecting the top flows on the network with very high probability.

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