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Debraj Roy

Publications and source records attributed to Debraj Roy.

17 recordsLinked to original sources

Poverty traps are rare, but trappedness isn't

The persistence of poverty is not well explained by who is poor. We argue the relevant object of measurement is trappedness--expected escape time from deprivation--which varies systematically across institutional environments and is invisible to standard poverty indices. Using Markov chains estimated on twenty years of longitudinal data from 27 European countries, we show that countries with identical deprivation rates differ in escape times by up to fourfold. These differences are not explained by household characteristics alone: exogenous shocks reshape welfare landscapes differently across countries, with divergence tracking welfare regime architecture rather than household composition. The mechanism is behavioural: health constrains a household's capacity to convert income gains into durable welfare improvement. Income transfers without health improvement fail to reduce poverty-return risk; combined interventions are super-additive across 28 countries, and the gap widens with transfer size. These findings dissolve the long-running poverty trap debate--studies that rejected traps measured the wrong dimension; studies that found them captured one projection of a multidimensional dynamic process. Trappedness is continuous, multidimensional, and institutionally shaped.

econ.GN

Cities cluster into growth regimes that propagate shocks

Economic growth is conventionally analyzed at the national level, yet cities generate the bulk of global output. Here we construct GDP trajectories for 8,808 functional urban areas (FUAs) across 165 countries over 1993-2019 using satellite-derived nighttime light data and identify 17 distinct, persistent growth regimes through clustering of full temporal trajectories. Rather than converging toward a common frontier, FUAs inhabit distinct economic niches-analogous to ecological niches-defined by shared volatility profiles, shock responses, and long-run dynamics that transcend national boundaries. Cities within the same country frequently belong to different regimes, while structurally similar cities on different continents share the same one; regime membership explains 16% of within-country growth variance beyond country fixed effects. National-level convergence emerges as an aggregation artifact: conditional convergence operates within regimes, not globally. A directed propagation network reveals that shocks transmit along lines of structural similarity rather than geographic proximity, with advanced economies exporting disturbances and emerging economies absorbing or amplifying them. Within-country spatial inequality declines with industrialization maturity, consistent with growth initially concentrating in leading cities before diffusing across the urban system. The global economy is better understood as an ecology of heterogeneous urban growth regimes than as a collection of nations on a shared development path.

econ.GN

Measuring growth and convergence at the mesoscale

Global inequality has shifted inward, with rising dispersion increasingly occurring within countries rather than between them. Using 8,790 newly harmonised Functional Urban Areas (FUAs) - micro-founded labour-market regions encompassing 3.9 billion people and representing approximately 80% of global GDP - we show that national aggregates systematically, and increasingly, misrepresent the dynamics of growth, convergence, and structural change. Holding the underlying nighttime-lights GDP raster (1992-2019) fixed while varying the unit of aggregation (ADM0-ADM3, FUA), we isolate the contribution of the Modifiable Areal Unit Problem directly in the growth literature. Three results follow. First, where inequality is located is unit-dependent: FUAs recover the most stable income-inequality relationship, corroborated by independent wealth data. Second, estimated beta-convergence is scale-sensitive, and FUAs exhibit a discrete jump in convergence strength relative to administrative units of comparable population. Third, we find no poverty trap at the urban scale: expected growth remains positive throughout the income distribution, while the middle-income acceleration flattens over time. The cross-country convergence debate has been conducted on national aggregates, yet nations are political containers rather than economic units, and measured relationships, including the convergence coefficient, depend on the spatial unit of analysis.

econ.GN

Cognitive biases shape the evolution of zero-sum norms

Why do maladaptive perceptions and norms, such as zero-sum interpretations of interaction, persist even when they undermine cooperation and investment? We develop a framework where bounded rationality and heterogeneous cognitive biases shape the evolutionary dynamics of norm coordination. Extending evolutionary game theory with quantal response equilibria and prospect-theoretic utility, we show that subjective evaluation of payoffs systematically alters population-level equilibrium selection, generating stable but inefficient attractors. Counterintuitively, our analysis demonstrates that the benefit of rationality and the cost of risk aversion on welfare behave in nonmonotone ways: intermediate precision enhances coordination, while excessive precision or strong loss aversion leads to persistent lock-in at low-payoff and zero-sum equilibria. These dynamics produce an endogenous equity-efficiency trade-off: parameter configurations that raise aggregate welfare also increase inequality, while more equal distributions are associated with lower efficiency. The results highlight how distorted payoff perceptions can anchor societies in divergent institutional trajectories, offering a behavioral-evolutionary explanation for persistent zero-sum norms and inequality.

econ.GN

Emergent poverty traps and inequality at multiple levels impedes social mobility

Eradicating extreme poverty and inequality are the key leverage points to achieve the seventeen Sustainable Development goals. Yet, the reduction in extreme poverty and inequality are vulnerable to shocks such as the pandemic and climate change. We find that that these vulnerabilities emerge from the interaction between individual and institutional mechanisms. Individual characteristics like risk aversion, attention, and saving propensity can lead to sub-optimal diversification and low capital accumulation. These individual drivers are reinforced by institutional mechanisms such as lack of financial inclusion, access to technology, and economic segregation, leading to persistent inequality and poverty traps. Our experiments demonstrate that addressing above factors yields 'double dividend' - reducing poverty and inequality within-and-between communities and create positive feedback that can withstand shocks.

econ.GN

Symmetricity of rings relative to the prime radical

In this paper, we introduce and study a strict generalization of symmetric rings. We call a ring $R \,\,\, 'P-symmetric'$ if for any $a,\, b,\, c\in R,\, abc=0$ implies $bac\in P(R)$, where $P(R)$ is the prime radical of $R$. It is shown that the class of $P$-symmetric rings lies between the class of central symmetric rings and generalized weakly symmetric rings. Relations are provided between $P$-symmetric rings and some other known classes of rings. From an arbitrary $P$-symmetric ring, we produce many families of $P$-symmetric rings.

math.RA

An exploratory factor analysis model for slum severity index in Mexico City

In Mexico, 25 per cent of the urban population now lives in informal settlements with varying degree of depravity. Although some informal neighbourhoods have contributed to the upward mobility of the inhabitants, the majority still lack basic services. Mexico City and the conurbation around it, form a mega city of 21 million people that has been growing in a manner qualified as "highly unproductive, (that) deepens inequality, raises pollution levels" and contains the largest slum in the world, Neza-Chalco-Izta. Urban reforms are now aiming to better the conditions in these slums and therefore it is very important to have reliable measurement tools to assess the changes that are undergoing. In this paper, we use exploratory factor analysis to define an index of depravity in Mexico City, namely the Slum Severity Index (SSI), based on the UN-HABITATs definition of a slum. We apply this novel approach to the Census survey of Mexico and measure the housing deprivation levels types from 1990 - 2010. The analysis highlights high variability in housing conditions within Mexico City. We find that the SSI decreased significantly between 1990 - 2000 due to several policy reforms, but increased between 2000 - 2010. We also show correlations of the SSI with other social factors such as education, health and migration. We present a validation of the SSI using Grey Level Co-occurrence Matrix (GLCM) features extracted from Very-High Resolution (VHR) remote-sensed satellite images. Finally, we show that the SSI can present a cardinally meaningful assessment of the extent of the difference in depravity as compared to a similar index defined by CONEVAL, a government institution that studies poverty in Mexico.

stat.AP

Vacuum energy in asymptotically flat 2+1 gravity

We compute the vacuum energy of three-dimensional asymptotically flat space based on a Chern-Simons formulation for the Poincare group. The equivalent action is nothing but the Einstein-Hilbert term in the bulk plus half of the Gibbons-Hawking term at the boundary. The derivation is based on the evaluation of the Noether charges in the vacuum. We obtain that the vacuum energy of this space has the same value as the one of the asymptotically flat limit of three-dimensional anti-de Sitter space.

hep-th

Effects of curvature and gravity from flat spacetime

We study some aspects of gravity in relation to flat spacetime. At first, we study an accelerated observer in Minkowski space as a quantum tunnelling problem in Rindler space. Both Bosonic and Fermionic modes are calculated to construct a reduced density matrix of particles tunnelling out across the accelerated Rindler horizon, giving a thermal spectrum characterized by a temperature proportional to the local acceleration - Unruh temperature. So, we calculate both the spectrum and temperature from within the tunnelling framework. In another direction, following Utiyama-Sciama-Kibble, we localise the Poincare group to obtain a Poincare gauge theory (PGT) of gravity. It had been pointed before in the literature, that the Poincare symmetries seemed to be recoverable canonically only on-shell. This would however mean existence of two independent sets of symmetries, each by itself having number of gauge parameters equal to the Poincare group, implying an apparent doubling of symmetries. To resolve this, we first start by a constraint analysis and construct the first-class gauge generator through an explicitly off-shell algorithm. We investigate both the Mielke-Baekler 3d model and a PGT formulation of New-Massive gravity. Next, we carefully study the symmetries and corresponding Noether identities to show that the difference between the two sets is a `trivial symmetry.' These is a transformation of fields that is not a true gauge symmetry as it gives rise to no new gauge degeneracy in defining physical states.

gr-qc

Trivial symmetries in a 3D topological torsion model of gravity

We study the gauge symmetries in a Mielke-Baekler type model of gravity in 2+1 dimensions. The model is built in a Poincare gauge theory framework where localisation of Poincare symmetries lead to gravity. However, explicit construction of gauge symmetries in the model through a Hamiltonian procedure yields an apparently different set of symmetries, as has been noted by various authors. Here, we show that the two sets of symmetries are actually equivalent in a canonical sense, their difference being just a set of trivial symmetries.

gr-qc

Poincaré gauge symmetries, hamiltonian symmetries and trivial gauge transformations

We resolve a problem of finding the Poincare symmetries from hamiltonian gauge symmetries constructed through a canonical procedure of handling constrained systems. Through the use of Noether identities corresponding to the symmetries, we motivate a procedure of finding the map between the hamiltonian and Poincare gauge parameters. Using this map, we show that the Poincare and hamiltonian gauge symmetries are equivalent, modulo trivial gauge transformations.

gr-qc

Hamiltonian analysis of symmetries in a massive theory of gravity

We construct the generator of hamiltonian gauge symmetries in a 2+1 dimensional massive theory of gravity, proposed recently, through a systematic off-shell algorithm. Using a field dependant map among gauge parameters we show that the symmetries obtained from this generator are on-shell equivalent to the Poincaré gauge symmetries. We also clarify certain subtle issues concerning the implementation of this map.

gr-qc

Lagrangian generators of the Poincare gauge symmetries

We have systematically computed the generators of the symmetries arising in Poincare gauge theory formulation of gravity, both in 2+1 and 3+1 dimensions. This was done using a completely Lagrangian approach. The results are expected to be valid in any dimensions, as seen through lifting the results of the 2+1 dimensional example into the 3+1 dimensional one.

gr-qc

Symmetries of topological gravity with torsion in the hamiltonian and lagrangian formalisms

A systematic analysis of the symmetries of topological 3D gravity with torsion and a cosmological term, in the first order formalism, has been performed in details - both in the hamiltonian and lagrangian formalisms. This illuminates the connection between the symmetries of curved spacetime (diffeomorphisms plus local Lorentz transformations) with the Poincare gauge transformations. The Poincare gauge symmetries of the action are shown to be inequivalent to its gauge symmetries. Finally, the complete analysis is compared with the metric formulation where the diffeomorphism symmetry is shown to be equivalent to the gauge symmetry.

gr-qc

The Unruh thermal spectrum through scalar and fermion tunneling

The thermal spectrum seen by accelerated observers in Minkowski space - known as the Unruh effect - is derived within the tunneling mechanism. This is a new result in this mechanism and it completes the treatment of Unruh effect via tunneling. Both Bose-Einstein and Fermi-Dirac spectrum is derived by considering tunneling of scalar and spin half particles respectively, across the accelerated Rindler horizon. Full solutions of Klein-Gordon and Dirac equations in the Rindler metric are employed to achieve this, instead of approximate solutions.

hep-th

Corrections to Unruh effect in tunneling formalism and mapping with Hawking effect

We consider coordinate systems adapted to accelerated observers, construct a generalised Rindler metric and then adopt a specific form of it to compute the semiclassical Unruh temperature, using a WKB approximation within a Hamilton Jacobi analysis in the tunneling picture. Corrections to this temperature are next computed by going beyond the usual WKB approximation. A connection of the corrected Unruh temperature with the Hawking temperature is established. This connection is also explained through the method of Global Embedding Minkowski Spacetime (GEMS).

hep-th